BBC News NI takes a look at significant events involving dissident republicans since March 2009.
The device was found in a parked car and was described by detectives as in "an advanced state of readiness" and was made safe by Army technical officers.
It contained commercial explosives which could have been triggered by a command wire.
During the searches, police were attacked with stones and petrol bombs.
A mortar bomb was left near a police station in Church View, Strabane on Saturday 7 September. Local homes were evacuated and Army technical officers made the device safe.
Police said the device had been an attempt to target police officers but that it could have killed or seriously injured anyone in the vicinity.
A 33-year-old man was arrested under terrorism legislation but was released after questioning.
A bomb explodes near Wattlebridge in County Fermanagh, on Monday 19 August.
Police say it was an attempt to lure officers to their deaths. Initially, a report received by police suggested that a device had been left on the Wattlebridge Road.
Police believe that a hoax device was used to lure police and soldiers into the area in order to catch them by surprise with a real bomb on the Cavan Road.
Chief Constable Simon Byrne later blames the Continuity IRA for the attack.
Dissident republicans try to murder police officers during an attack in Craigavon, County Armagh, the Police Service of Northern Ireland (PSNI) says.
A long bang is heard on the Tullygally Road and a "viable device" is later found.
Police say they believe the attack was set up to target officers responding to a call from the public.
The Irish News says it had issued a statement to the newspaper using a recognised codeword.
Police had said they believed "violent dissident republicans" were behind the attack.
A journalist is shot dead while observing rioting in the Creggan area of Londonderry.
Lyra McKee's murder comes days before the anniversary of the 1916 Easter Rising.
Police blame the 29-year-old's killing on dissident republicans.
The previous week a horizontal mortar tube and command wire were found in Castlewellan, County Down.
The PSNI say the tube contained no explosive device and it was likely to be collected for use elsewhere
Five small explosive packages are found at locations across Great Britain and the Republic of Ireland.
The letter bombs have been sent in the post to Waterloo Station, buildings near Heathrow and London City Airport and the University of Glasgow. A further device was found at a post depot in County Limerick.
The New IRA says it was behind the letter bombs, according to the Irish News. A recognised code word is used.
A bomb placed inside a van explodes in the centre of Londonderry.
The blast happens on a Saturday night outside Bishop Street Courthouse.
The PSNI say the attack may have been carried out by the New IRA, adding that a pizza delivery man had a gun held to his head when his van was hijacked for the bombing.
A stash of bullets and guns believed to belong to dissident republicans explodes after being left on top of a hot boiler at a house in west Belfast.
Responding to reports of a house fire in Rodney Drive, police and firefighters discover two AK-47s; two sawn-off shot guns; a high-powered rifle with a silencer and three pipe bombs.
Police blame the New IRA, and say the weapons are believed to have been used in previous attempts to murder police officers in Belfast in 2015 and 2017.
Police say a "significant amount of dangerous weapons" were seized during a 12-day search operation in counties Armagh and Tyrone.
Thirteen searches took place on land and properties in Lurgan and Benburb from 29 April to 11 May.
The weapons including two shotguns, four handguns, explosives, ammunition and a suspected mortar tube.
Police believe the munitions belonged to two dissident republican paramilitary groups - Arm Na Poblachta. (Army of the Republic) and the Continuity IRA.
Petrol bombs and stones are thrown at police vehicles during an illegal dissident republican parade in Londonderry on 2 April.
About 200 people attended the Easter Rising 1916 commemoration parade in the Creggan estate on Monday.
On 1 April, seven men are charged in connection with an illegal republican Easter parade in Lurgan in County Armagh.
Eight masked men wearing paramilitary-style uniforms were arrested on Levin Road on 31 March.
A ninth person was arrested on suspicion of assaulting a police officer and obstruction.
Dissident republicans may have been behind the murder of a man in west Belfast, police say.
Raymond Johnston, 28, was shot dead in front of an 11-year-old girl and his partner at a house in Glenbawn Avenue on 13 February.
Police say the main line of inquiry was that Mr Johnson was murdered by dissidents.
Dissident republican paramilitary group, Óglaigh na hÉireann (ONH), declares a ceasefire.
In a statement, it said that "at this time the environment is not conducive to armed conflict".
The group said it would "suspend all armed actions against the British state" with immediate effect.
It was responsible for a number of high-profile attacks, including the attempted murder of police officer Peadar Heffron and a bomb attack at Palace barracks in Holywood.
The Catholic Bishop of Derry condemns a death threat from dissident republicans against a Protestant man who works in the city's Creggan estate.
The 64-year-old man who has been threatened works at an allotment in the Ballymagowan area.
A gun is seized in west Belfast on 3 August as part of a police investigation into dissident republican activity.
Police said the gun and a number of other items, including money and a small quantity of suspected drugs, were taken for examination following searches in the Andersonstown area.
Royal Marine Ciarán Maxwell pleads guilty to offences related to dissident republican terrorism, including bomb-making and storing stolen weapons.
The County Antrim man had compiled a library of terrorism documents, including instructions on how to make explosives and tactics used by terrorist organisations.
He also had maps, plans and lists of potential targets for a terrorist attack, and a stash of explosives in purpose-built hides in England and Northern Ireland.
His sentencing is currently taking place at the Old Bailey in London.
A bomb explodes outside the home of a serving police officer in Londonderry on 22 February as Army experts try to defuse it.
The device, which police described as more intricate than a pipe bomb, was reportedly discovered under a car in Culmore in the city.
Children were in the area at the time, police said.
A gun attack on a 16-year-old boy in west Belfast on 16 February was "child abuse," a senior police officer said.
The attack followed a similar one the previous night, when a man was shot in the legs close to a benefits office on the Falls Road.
A police officer is injured in a gun attack at a garage on north Belfast's Crumlin Road on 22 January.
Police said automatic gunfire was sprayed across the garage forecourt in a "crazy" attack.
A 36-year-old man is arrested and police say the main line of inquiry is "violent dissident republicans".
The number of paramilitary-style shootings in west Belfast doubled in 2016 compared to the previous year, according to police figures.
The figures do not take into account three shootings in Belfast's Turf Lodge area since the start of January.
On 15 January, police say a bomb discovered during a security operation in Poleglass, west Belfast, was "designed to kill or seriously injure police officers".
A judge on 6 January revokes the bail of a County Tyrone man facing trial on charges linked to the murder of prison officer David Black.
Damien Joseph McLaughlin, 40, of Kilmascally Road near Ardboe, is due to stand trial in February.
The court is told Mr McLaughlin had not been seen by police since November.
A 45-year-old mechanic caught at a bomb-making factory on a farm will spend 11 years behind bars.
Barry Petticrew was arrested in October 2014 after undercover police surveillance on farm buildings near Kinawley, County Fermanagh.
Police found pipes, timer units, ammunition and high grade explosives in the buildings.
On 6 December, a 25-year-old dissident republican is jailed in Dublin for five years.
Donal Ó Coisdealbha from Killester, north Dublin was arrested on explosive charges in the run-up to the visit of Prince Charles to Ireland in 2015.
He was arrested during a Garda operation when explosive devices, improvised rockets, detonators, timing units and Semtex were discovered.
A man who admitted taking part in a paramilitary shooting in Belfast is sentenced to five years in jail and a further five years on licence.
Patrick Joseph O'Neill, of no fixed address, was one of three masked men who forced their way into the victim's home in Ardoyne in November 2010.
The man was shot several times in the legs and groin in front of his mother, who fought back with kitchen knives.
The dissident republican group Óglaigh na hÉireann claimed responsibility for the shooting shortly after it took place.
West Belfast man Joe Reilly, 43, is shot dead in his Glenwood Court, Poleglass home on 20 October.
It is understood a second man who was in the house was tied up by the gang. The shooting was the second in the small estate in less than a week - the other victim was shot in the leg.
Police later say they believe the the murder was carried out by a paramilitary organisation and there may have been a drugs link.
Four men are charged on 26 September after police recovered an armour-piercing mortar during searches in Lurgan.
They were arrested on 21 September by police investigating dissident republican activity in the area.
Three men, aged 22, 24 and 46, are charged with targeting a former member of the security forces in the Craigavon area.
A fourth, aged 22, is charged with the attempted murder of police officers.
Dissident republicans form a new political party called Saoradh - the Irish word for liberation.
Several high-profile dissidents from both sides of the border were among about 150 people at its first conference in Newry.
Royal Marine Ciaran Maxwell appears in court in England charged with terrorism, fraud and drugs offences.
The charges include making explosives and storing them in hides in England and Northern Ireland.
He is also accused of possession of an adapted PSNI pass card and items of PSNI uniform. He denies the charges and is remanded in custody.
On 6 September, searches in County Antrim linked to the investigation of Mr Maxwell turn up a "significant amount of terrorist material", police say.
On 24 August serving Royal Marine Ciaran Maxwell, who is originally from Larne, is arrested in Somerset.
His arrest is connected to the discovery of two arms dumps near Larne earlier in the year.
The 30-year-old is suspected of preparing for acts of terrorism.
A major arms haul believed to be connected to dissident republicans is uncovered in County Armagh on 5 August.
Firearms and munitions were found by police during a two-day search operation in the grounds of a former convent on the outskirts of Lurgan.
The weapons that were discovered are believed to belong to the group known to as the New IRA.
Police say they are investigating if a bomb found in Lisburn on 31 July had fallen from a vehicle.
A controlled explosion was carried out on the object after it was found in Market Place.
It was made safe and removed for examination during a security alert which lasted several hours.
Police believe that pipe bombs found in Londonderry on 17 June could be linked to "violent dissident republican terrorism".
The two devices were discovered in the Highmoor Road area of the city.
The discovery of arms in a County Antrim forest on 17 May was one of the most significant in recent years, police say.
A "terrorist hide" was uncovered at Capanagh Forest near Larne after two members of the public found suspicious objects in the woods on Saturday.
Some of the items found included an armour-piercing improvised rocket and two anti-personnel mines.
The threat level from Northern Ireland-related terrorism in Great Britain is raised from moderate to substantial.
It means an attack in England, Scotland or Wales is "a strong possibility".
Home Secretary Theresa May says the level, set by security service MI5, "reflects the continuing threat from dissident republican activity".
Fifteen men are arrested in Strabane after paramilitary displays at the funeral of Dublin murder victim Michael Barr.
Barr, said to be a member of the New IRA, was shot dead in the Sunset House pub in Dublin on 25 April.
A man dies after being shot three times in the leg in an alleyway at Butler Place, north Belfast, on Friday 15 April.
Michael McGibbon, 33, was taken to the Royal Victoria Hospital in Belfast, where he later died.
Police have said Mr McGibbon had contacted them to say two masked men had arrived at his house on the evening of Thursday 14 April.
The men asked him to come out of the house but he refused and the men told him they would come back.
Mr McGibbon's murder has been referred to the Police Ombudsman for Northern Ireland.
Police say his killing carried the hallmarks of a paramilitary murder.
The device exploded under the 52-year-old officer's van as he drove over a speed ramp at Hillsborough Drive on 4 March.
Days later, a dissident republican group widely referred to as the new IRA said it carried out the attack.
In the immediate aftermath of the bombing, the Police Service of Northern Ireland say they are "deeply concerned" about the threat posed by dissident republicans ahead of the centenary of the 1916 Easter Rising later in the month.
Mr Ismay was thought to have been making a good recovery from his injuries, but was rushed back to hospital on 15 March, where he died.
A post-mortem examination found his death was as a "direct result of the injuries" he sustained in the bomb.
In a statement to the BBC, a man claiming to speak on behalf of the Continuity IRA (CIRA) claims its members were responsible for a fatal gun attack on a Dublin hotel during a weigh-in for a boxing match, but Irish police (Gardaí) say they believe the motive for the killing was a criminal feud.
The alleged CIRA spokesman claimed to the BBC that its members had shot dead 33-year-old David Byrne because he had been involved in the killing of Real IRA leader Alan Ryan in Dublin in 2012.
Days later, police fears of a criminal feud appear to be realised as taxi driver Eddie Hutch is shot dead in a suspected revenge attack in his flat in Dublin's north inner city.
In mid-February, The Sunday Times newspaper alleges that a CIRA paramilitary from Northern Ireland is believed to have been among the six gunmen involved in the hotel shooting at the boxing weigh-in.
On the last day of the month, Alan Ryan's brother, Vinnie Ryan, is shot dead in Finglas, north Dublin. Irish police say Vinnie Ryan was also a well-known dissident republican, but they say they are not linking his murder to the gangland feud that killed David Byrne and Eddie Hutch.
Dissident republicans have been dealt "a significant blow" by a weapons and explosives find in the Republic of Ireland, the Irish police (Gardaí) say.
The weapons, including AK-47 assault rifles, mortars, detonators and other bomb parts, were discovered in County Monaghan, close to the border with Rosslea in County Fermanagh, on 1 December.
Insp James O'Leary, of Monaghan police station, said the weapons would have posed "a very significant threat to security personnel on both sides of the border".
On 15 December, a further arms find, described as a "significant cache" by Irish state broadcaster RTÉ, is made in County Louth.
It has reported that the haul included AK47 assault rifles, mortars, explosive material, detonators, other bomb components and at least one revolver.
It follows police searches at a home and lands in Jenkinstown, close to the border with Northern Ireland.
A gun attack on police officers in west Belfast on 26 November, in which up to eight shots were fired, is being treated attempted murder.
A number of shots struck the passenger side of a police car parked at Rossnareen Avenue.
Two officers who were in the car were not injured but were said to have been badly shaken.
Police describe it as a "mindless, reckless attempt to kill officers".
On 23 November, police seize bomb-making components and ammunition during searches at Broom Close in Twinbrook and Glenwood Walk, Poleglass, in west Belfast.
The haul includes 700 rounds of assorted ammunition, seven mercury tilt switches, detonator cord, firework powder and an assault rifle magazine.
The threat to the lives of police officers from dissident republicans in the north west of Northern Ireland remains severe, a senior officer says on 6 October.
Supt Mark McEwan said that from September 2014 there had been 15 bomb incidents in the Derry City and Strabane District council area.
They included seven attacks on the police.
On 10 October, a bomb is found in the grounds of a Londonderry ahead of a police recruitment event.
The police recruitment event was cancelled. Two other police recruitment events in Belfast and Omagh went ahead despite bomb alerts at the planned venues.
On 15 October, police said they believe that a bomb found in north Belfast may have fallen from a car belonging to a man with connections to the armed forces.
The device was discovered at Linden Gardens, off the Cliftonville Road.
It is not clear if the intended target was passing through the area or visiting someone there.
Sinn Féin MLA Gerry Kelly said a young boy had kicked the bomb while it lay on the street.
On 16 October police said a "military-style hand grenade" was thrown at a patrol in Belfast as officers responded to reports of anti-social behaviour.
Police say the device, which failed to explode, was thrown at officers near Pottingers Quay.
Dissident republicans were suspected of being responsible for the attack.
Police say a mortar bomb found in a graveyard in Strabane, County Tyrone, on 1 August was an attempt to kill officers.
The device was positioned where it could be used to attack passing PSNI patrols, police said.
A bomb is found under a police officer's car in Eglinton, near Londonderry, on 18 June.
Police said the attack was a "clear attempt to murder police officers".
PSNI District Commander Mark McEwan said the wife of the officer concerned was also a member of the PSNI.
Two bombs found close to an Army Reserve centre in Londonderry were left about 20 metres from nearby homes.
The devices were left at the perimeter fence of the Caw Camp Army base and were discovered at 11:00 BST on 4 May.
The two bombs partially detonated.
About 15 homes in Caw Park and Rockport Park were evacuated during the security operation.
A device found in north Belfast on 1 May was a substantial bomb targeting police officers, the PSNI said.
A controlled explosion was carried out on the device at the Crumlin Road junction with Brompton Park.
The PSNI blamed dissident republicans for the bomb and said it could have caused "carnage".
Ch Supt Nigel Grimshaw said it was a "fairly substantial cylinder-type device" that was "designed to do one thing - kill".
On 28 April, a bomb explodes outside a probation office in Crawford Square, Londonderry.
Police said they were given an "inadequate" warning before the device went off.
No-one was injured.
A prominent dissident republican activist is remanded in custody charged in connection with comments he allegedly made at an Easter Sunday republican commemoration.
Damien 'Dee' Fennell, 33, from the Ardoyne area of north Belfast, is accused of encouraging people to commit acts of terrorism.
He is also accused of supporting a proscribed organisation.
It follows a speech he gave in Lurgan, County Armagh, earlier in the month.
A Londonderry man beaten with iron bars by a masked gang blames dissident republicans for the attack.
Gerald Lavey, 30, said his children clung to him during the attack by up to six men at his home at Ballymagowan Avenue, Creggan, on 31 March.
He said the gang dragged him from his living room to the front garden where he was beaten with iron bars and nails.
Hours after the attack, a wheelie bin was set alight next to the house.
On 26 March Derry men, William McDonnell, 28, from Culfdaff Gardens in the Creggan area, and Thomas Ashe Mellon, 39, from Rathmore Gardens, plead guilty to having a handwritten note which was being smuggled into Maghaberry Prison for dissident republican prisoners.
It was a handwritten note for a purpose connected with the commission, preparation or instigation of an act of terrorism.
A neighbour who went to help two men beaten with baseball bats in a paramilitary-style attack in Derry said they were left for dead.
The men were beaten with baseball bats and iron bars by a gang of six to eight masked men who broke into a flat at Ederowen Park in Galliagh on 15 March.
The victims suffered injuries to their heads, ribs and legs.
It is believed one of the masked gang had a gun.
A bomb is found is found during a security alert in the Curryneiran estate in Londonderry on 17 February.
Police said they believe the bomb was intended to kill officers and that those who had left it showed a "callous disregard for the safety of the community and police officers".
Some residents had to be moved out of their homes overnight. The alert started after phone calls claiming an explosive device had been left in a laneway.
At least 40 dissident republican prisoners are involved in an incident at Maghaberry Prison on 2 February.
Prison management withdrew staff from the landings in Roe House housing dissidents.
A protest, involving about 200 people, took place outside the prison in support of the republican prisoners.
Two men are arrested by Irish police investigating dissident activity, in Dundalk, County Louth on 13 January.
A man in 40s was detained and a rifle recovered after a car was stopped and searched on the Point Road on Tuesday.
A man in his late 50s was later arrested during a follow-up search at a house also in Dundalk.
Police described the original stop and search of the car as a planned operation.
On 8 January, the head of MI5 says most dissident republican attacks in Northern Ireland in 2014 were foiled.
Andrew Parker said of more than 20 such attacks, most were unsuccessful and that up to four times that amount had been prevented.
He made the remarks during a speech in which he gave a stark warning of the dangers UK is facing from terrorism.
He said it was "unrealistic to expect every attack plan to be stopped".
On 17 December, an eighth person appears in court charged over an alleged Continuity IRA meeting in Newry.
Twelve people were arrested in Ardcarn Park in the city on 10 November.
There is a "strong possibility" that dissident republicans will carry out attacks in the run-up to Christmas, a senior police chief warns.
Assistant Chief Constable Will Kerr said violence from such groups posed a "severe threat" in Northern Ireland.
"They are dangerous, they could do real harm and we will be working extremely hard over Christmas to tackle this threat," he said.
On 22 November, a 29-year-old man is charged with having a firearm and ammunition with intent to endanger life.
He was arrested two days earlier on the Grosvenor Road in west Belfast on Thursday after police stopped a taxi and recovered an assault rifle and ammunition.
Dissidents are blamed for shooting a 29-year-old man at a house in Londonderry.
It happened at a house in Cecilia's Walk in the Creggan area at about 18:00 GMT 20 November.
A baby, a five-year-old child, and the man's partner were in the house when masked gunmen burst into the kitchen.
Dissident republicans are believed to have used a home-made rocket launcher in an attack on a police Land Rover at Twaddell Avenue in North Belfast on Sunday 16 November .
It struck the Land Rover and caused some damage, but no-one was injured.
Police described the attack as a "cold, calculated attempt to kill police officers".
Irish police describe the seizure of guns and bomb-making material during searches in Dublin on 15 November as a "major setback" for dissident republicans.
An AK47 rifle, a sawn-off shotgun and a number of semi-automatic pistols were found in searches in the Ballymun, East Wall and Cloughran areas of Dublin.
The Irish Army carried out a controlled explosion at one search location where bomb components were discovered.
Two men in their 50s were arrested.
Police investigating "violent dissident republican activity" charge seven men with terrorism offences.
On 14 November, Derry City Council holds a meeting over death threats against community safety wardens, believed to have been made by dissident republicans.
The men were arrested at a house in Ardcarne Park in Newry, County Down, on 10 November.
The men were aged 30, 43, 44, 58, 59, 73 and 75.
Five of them were charged with directing terrorism.
On 5 November, a Derry councillor and leading dissident republican is given a six-month prison sentence for causing criminal damage to the city's historic walls.
Gary Donnelly, 43, from Iniscairn Road in the Creggan area, was charged with painting political slogans on the city's walls in February.
Liam Brogan, 51, and Terry Porter, 56, both from Carnhill, also received six-month prison sentences.
A device that hit a police vehicle in Londonderry on 2 November is understood to have been a mortar, fired by command wire.
Dissident republicans were responsible for the attack, police have said.
The attack happened on Circular Road in the Creggan Heights area at about 20:40 GMT.
Police foil an attempted bomb attack in Strabane's Ballycolman estate on 23 October.
Officers were lured to Ballycolman estate on 23 October to investigate reports of a bomb thrown at a police patrol vehicle the previous night.
The alert was a hoax but then a real bomb, packed with nails, was discovered in the garden of a nearby house.
Explosives and other weapons found in County Fermanagh on 10 October represented "a threat to the community", Northern Ireland's justice minister says.
Police said a "significant" amount of explosives had been found and linked the weapons to dissident republicans.
Buildings, vehicles and fields were searched at a farm in Kinawley.
Dissident republicans claim responsibility for a device that partially exploded outside an Orange hall in County Armagh on 29 September.
In a phone call to the Irish News, a group calling itself The Irish Volunteers admitted it placed the device at Carnagh Orange hall in Keady.
Three men and two woman are jailed for taking part in a dissident republican training camp.
Sean Kelly, 49, of Duneane Crescent, Toomebridge, was sentenced to a minimum of five years in prison, with an order to serve five more on licence.
Sharon Rafferty, 39, of Cabhan Aluinn, Pomeroy, was sentenced to four years in jail and four on licence.
Brothers Gavin Joseph Coney, 37, of Gorticashel Road, Omagh, and Terence Aiden Coney, 36, of Malabhui Road, Carrickmore, were jailed for five years and nine months.
On 16 June, police investigating dissident republican activity say they have recovered two suspected pipe bombs in County Tyrone.
Three men and a woman admit charges over a dissident republican training camp in County Tyrone.
It was found at Fourmil Wood, on the outskirts of Omagh, County Tyrone, in March 2012.
Sharon Rafferty, 38, from Cabhan Aluinn, Pomeroy, Sean Kelly, 48, from Duneane Crescent, in Toomebridge and brothers Aidan Coney, 35, from Malabhui Road, Carrickmore and Gavin Joseph Coney, from Gorticashel Road, Omagh will be sentenced at a later date.
On 9 June, a man appears at Londonderry Magistrates Court on charges linked to dissident republican activity in the city.
Thomas Ashe Mellon, 38, of Rathmore Road, Derry, is charged with membership of a proscribed organisation, namely the IRA, and with directing the activities of the IRA.
On the night of 29 May, a masked man threw what police have described as a "firebomb" into the reception area of the Everglades Hotel, in the Prehen area of Londonderry.
The hotel was evacuated and the device exploded a short time later when Army bomb experts were working to make it safe.
No-one was injured in the explosion but the reception was extensively damaged.
The man who took the bomb into the hotel said he was from the IRA.
Two men jailed for the dissident republican murder of policeman Constable Stephen Carroll in Craigavon lose an appeal against their convictions.
Brendan McConville, 42, of Glenholme Avenue in Craigavon, and 22-year-old John Paul Wootton, from Colindale in Lurgan, are serving life sentences.
On 25 March, five men are arrested after a suspected bomb was discovered by police in County Louth in the Republic of Ireland.
The device was found in Kilcurry, north of Dundalk, near the border with Northern Ireland, as part of an investigation into dissident republican activity.
32 County Sovereignty Movement member Gary Donnelly is elected to the new Derry and Strabane super council.
On 8 May, Dissident republican Seamus McLaughlin pleads guilty to charges connected to a foiled mortar bomb attack on a police station in March 2013.
He pleaded guilty to having four "ready to deploy" mortars and an improvised explosive incendiary device with intent to endanger life.
A substantial amount of explosives are found on 1 May by police investigating dissident republican activity in Northern Ireland.
The discovery was made during searches of a flat in the New Lodge area of north Belfast.
A 47-year-old man is arrested and later charged over the find.
A prominent dissident republican is shot dead in west Belfast on 18 April.
Tommy Crossan was shot a number of times at a fuel depot off the Springfield Road.
Mr Crossan, 43, was once a senior figure in the Continuity IRA. It is believed he had been expelled from the group some years ago after falling out with other dissidents.
On 1 April, dissident republicans are blamed for leaving a viable pipe bomb at Townsend Street in Strabane.
Police say that a bomb found at a County Tyrone golf course had the capability to kill or cause serious injury.
Bomb disposal experts made the device safe after it was discovered at Strabane Golf Club on 31 March.
The operation followed information received by police that a device had been left in the Ballycolman Road area.
An undercover surveillance operation is believed to have led to the seizure of an improvised mortar bomb in Belfast on 28 March.
Police believe the operation may have foiled an attack.
The bomb and a command wire were found in a holdall when police stopped a man at the junction of Shaw's Road and Glen Road in the west of the city.
A Belfast man with known dissident republican links died on 28 March a week after he was shot in a Dublin gun attack.
Declan Smith, 32, was shot in the face by a lone gunman as he dropped his child at a crèche on Holywell Avenue, Donaghmede.
He was wanted by police in Northern Ireland for questioning about the murder of two men in Belfast in 2007.
Mr Smith was originally from west Belfast but had moved to live in north Dublin.
A bomb explodes inside a car parked at Carrickreagh Gardens in the Creggan area of Londonderry on 26 March.
The man who owns the car said he did not believe dissident republicans were responsible. However, SDLP MLA Pat Ramsey said the attack "bears the hallmarks of the dissident group formerly known as Republican Action Against Drugs".
On the night of 14 March, dissidents use a command wire to fire a mortar at a police Land Rover on the Falls Road in west Belfast.
The device hit the Land Rover, but police said it caused minimal damage.
No-one was injured in the attack, but as well as the police patrol, a car containing a Filipino family was caught up in the attack.
The dissident group calling itself the New IRA said it carried out the attack and claimed the mortar used contained the military explosive Semtex and a commercial detonator.
They claim both were newly acquired - in other words, not from old supplies previously under the control of the Provisional IRA.
Earlier that day, an under-car bobby-trap bomb was made safe after being found on Blacks Road in west Belfast.
The road was closed and residents had to leave their homes while the device, which is believed to have fallen off a vehicle, was made safe by the Army.
Two letter bombs were found at postal sorting offices in Lisburn and Londonderry on 7 March.
Both were addressed to the Maghaberry Prison, the largest jail in Northern Ireland.
Seven letter bombs delivered to army careers offices in England bear "the hallmarks of Northern Ireland-related terrorism", Downing Street said.
The packages were sent to offices in Oxford, Slough, Kent, Brighton, Hampshire and Berkshire.
Three men are arrested and "a large sum" of counterfeit money seized on 3 February by police investigating dissident republican activity in Dublin.
Four men who were in a car in a which a gun was found are jailed.
Mark McGuigan was sentenced to 12 years, Daniel John Turnbull to nine years, Martin McLoone to eight years and Darryn Patrick McCallion to seven years.
Each will serve half the term in custody and the rest on licence.
During follow-up searches police recovered a sub-machine gun, a hand gun and ammunition from a vehicle belonging to Daniel Turnbull.
Police said they believed the weapons were intended to be used in a dissident republican attack.
On 9 January, it is announced that more than 1,000 prison service staff in Northern Ireland are to receive special annual danger money payments because of the threat from dissident republicans.
An independent pay review body recommended that they should each be paid more than £1,300 a year on top of their normal salary.
On 7 January, Old Bailey bomber Marian McGlinchey is given a suspended sentence for aiding dissident republican terrorists.
McGlinchey, also known as Marian Price, admitted providing a mobile phone used to claim responsibility for the Real IRA murders of two soldiers at Massereene Army barracks in 2009.
She also admitted aiding and abetting the addressing of a meeting to encourage support for terrorism.
Shots are reportedly fired at Lisnaskea police station in County Fermanagh on the night of 23 December. Dissident republicans are blamed for the attack.
Prominent republican Colin Duffy is one of three men who appear in court in Belfast on 17 December on dissident republican charges.
On 16 December a man apparently trying to plant a fire bomb in a golf store in Belfast city centre bursts into flames and runs from the shop with his clothes on fire.
On 13 December, a bomb in a sports bag explodes in Belfast's busy Cathedral Quarter.
About 1,000 people were affected by the alert, including people out for Christmas dinners, pub-goers and children out to watch Christmas pantos.
A telephone warning was made to a newspaper, but police said the bomb exploded about 150 metres away as the area was being cleared.
Dissident republican group, Óglaigh na hÉireann, said they were responsible.
On 5 December, two police vehicles are struck 10 times by gunfire from assault rifles while travelling along the Crumlin Road, near Brompton Park, in north Belfast.
One Kalashnikov-type weapon is recovered after the attack.
It is understood those behind the attack built a platform on Herbert Street, from where the shots were fired.
On the following night, two shots strike a PSNI Land Rover on patrol on the Suffolk Road between the Stewartstown and Glen Roads in west Belfast.
A bomb, containing 60kgs (132lbs) of home-made explosives, partially explodes inside a car in Belfast city centre on 24 November.
A masked gang hijacked the car, placed a bomb on board and ordered the driver to take it to a shopping centre.
It exploded as Army bomb experts prepared to examine the car left at the entrance to Victoria Square car park.
No-one was injured.
Old Bailey bomber Marian McGlinchey pleads guilty to providing a mobile phone linked to a Real IRA attack in which two soldiers were murdered.
McGlinchey, also known as Marian Price, admitted providing property for the purposes of terrorism.
The charge was connected to the attack on Massereene Army barracks in 2009.
She also admitted aiding and abetting the addressing of a meeting to encourage support for terrorism.
On 21 November, a bus driver is ordered to drive to a police station in Londonderry with a bomb on board.
A masked man boarded the bus in Ballymagroarty estate Wednesday and ordered the driver to go to Strand Road police station.
The bus driver drove a short distance to Northland Road, got her passengers off the bus and called the police.
A former police officer is the target of an under-car booby-trap bomb off the King's Road in east Belfast.
The man spotted the device when he checked under his vehicle at Kingsway Park, near Tullycarnet estate on 8 November.
The man was about to take his 12-year-old daughter to school.
Dissidents are blamed for a number of letter bomb attacks at the end of the month.
A package addressed to Secretary of State Theresa Villiers is made safe at Stormont Castle, two letter bombs addressed to senior police officers are intercepted at postal sorting offices, while, a similar device is sent to the offices of the Public Prosecution Service in Londonderry.
Five people with alleged links to dissident Irish republicanism appeared in court in Glasgow on 29 October charged with terror offences and conspiracy to murder.
On 18 October a "viable explosive device" is found during a security alert in Lurgan.
The alert in the Sloan Street area closed two schools, and caused widespread disruption in the County Armagh town. Police said they believe dissident republicans were responsible for planting the device.
Kevin Kearney, 46, is found dead in a lake in Alexandra Park, off the Antrim Road, north Belfast, on 9 October.
He had been shot dead the previous day. Dissident republicans said they killed Mr Kearney.
Four men have been arrested by police following a hoax bomb alert on the M1 motorway on 7 October.
The motorway was closed for a time between Belfast and Lisburn after a suspicious object was found on the Kennedy Way offslip.
An appeal court in Lithuania overturns the conviction of a man jailed for attempting to buy weapons for dissident republicans.
Michael Campbell was found guilty in October 2011 after an MI5 sting operation in 2008 recorded him attempting to buy explosives and guns.
He was originally sentenced to 12 years in prison. The appeal court judge found that prosecutors failed to prove his ties with the Real IRA.
A 45-year-old man is charged with possession of a firearm and ammunition in suspicious circumstances.
The charges are linked to an investigation into dissident republican terrorism in north Belfast.
Guns and ammunition are found in separate searches by police investigating dissident republican activity in Dublin and County Clare in the Republic of Ireland.
Footage appears to show a dissident republican gunman firing at police during rioting in the Ardoyne area of north Belfast on 12 July.
It shows the gunman firing towards police lines from within a crowd gathered at Brompton Park in Ardoyne.
After the last of 17 shots rings out, youths clap and cheer.
Irish police make what they say is their biggest ever find of dissident republican arms and explosives.
Guns, ammunition and 15kg of Semtex explosive are found on land at the Old Airport Road in Cloghran, north Dublin.
The arms include former Provisional IRA weapons, according to police.
Eight men appear before two special sittings of the Special Criminal Court in Dublin charged with offences linked to a police operation against dissident republicans in the city.
Seven arrested at a house in Tallaght on Wednesday were charged with membership of an unlawful organisation and have been remanded in custody.
At a separate sitting of the court a 45-year-old Dublin man was charged with IRA membership and possession of ammunition.
On 27 June, a 70-year-old man from west Belfast is sentenced to six and a half years for firearms and explosives offences.
Thomas Maguire, of Suffolk Drive, was arrested in August 2011, when police stopped his car following a car chase.
Dissident republicans issue a death threat against a woman journalist in Northern Ireland, according to a union.
The National Union of Journalists (NUJ) said the PSNI had informed the journalist about the threat.
A gun and ammunition are found by police investigating dissident republican activity in Cookstown, County Tyrone on 10 June.
Two police officers escape injury after two pipe bombs are thrown at them in north Belfast.
The officers were responding to an emergency 999 call in Ballysillan in the early hours of 28 May.
They had just got out of their vehicle on the Upper Crumlin Road when the devices were thrown. They took cover as the bombs exploded.
On 22 May police recover a gun during searches connected to dissident republican activity in the Short Strand area of east Belfast.
A bomb is removed from the Foxes Glen area of west Belfast on 17 May - the scene of a gun attack on police officers the previous day.
Up to six shots were fired as three officers got out of their vehicle in the area on Thursday afternoon. No-one was injured.
Sinn Fein says police warn Deputy First Minister Martin McGuinness of a renewed threat from dissident republicans
Police investigating dissident republican activity seize contraband cigarettes worth £300,000 in south Armagh. A total of £50,000 in cash was also recovered.
Detectives investigating dissident terrorist activity uncover guns and ammunition in Craigavon.
The weapons and other items had been hidden on waste ground in the Pinebank area.
A 50-year-old woman who shot dead an innocent man in Dublin because she mistakenly believed he was involved in the murder of a Continuity IRA leader is sentenced to life in prison on 10 April.
Rose Lynch told police she "executed" David Darcy in November of 2011.
Lynch described herself as "an IRA volunteer".
On 7 April two men from Derriaghy, County Antrim, are charged with possession of a firearm in suspicious circumstances.
The weapon was recovered during a security alert on the Barnfield Road in Lisburn following a police investigation into dissident republican activity.
On 1 April, police vehicles have come under attack from youths throwing stones and other missiles at a dissident republican Easter commemoration in Londonderry.
Chief Constable Matt Baggott says dissident republican groups are trying to outdo each other.
Mr Baggott said the groups are in competition when it comes to the number of attacks they carry out.
He said that the "recklessness of their attacks is beyond measure".
Police escape injury after a bomb in a bin exploded on the Levin Road in Lurgan on 30 March.
Officers were investigating reports of an illegal parade in when the device went off near a primary school.
Petrol bombs are thrown at police during follow-up searches in the Kilwilkie area.
Police say a bomb meant to kill or injure officers on the outskirts of Belfast on 9 March may have been detonated by mobile telephone.
Officers were responding to a call on Duncrue pathway near the M5 motorway when the bomb partially exploded.
On 4 March, four live mortar bombs which police said were "primed and ready to go" are intercepted in a van in Londonderry.
The van had its roof cut back to allow the mortars to be fired. Police say they believed the target was a police station.
Three men are arrested.
It is the first time dissidents have attempted this type of mortar attack.
On 2 March, police investigating dissident republican activity charged a 23-year-old man with possessing items likely to be of use to terrorists.
It was believed the arrest was linked to a security alert in Larne, County Antrim.
On 26 February, the police and Army recover a rocket launcher and a warhead during a search of a house in Hawthorn Street, west Belfast.
A PSNI spokesman says the weapons systems were "clearly intended to kill" and the recovery had "saved lives".
On 25 February, two Cork men appear before Dublin's Special Criminal Court charged with firearms offences and membership of a paramilitary organisation.
Brian Walsh, 43, and Anthony Carroll, 30, were arrested in Togher two days earlier when police stopped a car and recovered two handguns.
On 8 February, Irish police find rocket launchers and explosives after they stopped two cars on the N24 in County Tipperary.
Garda detectives say they believe the weapons were ultimately destined for Northern Ireland.
Three men are arrested at the scene. Two are charged with membership of an unlawful paramilitary organisation while the third man is released without charge.
At the end of the month, dissident republicans were blamed for two pipe bomb attacks in north Belfast within the space of 24 hours.
On 29 January, the dissident republican group, Oglaigh na hEireann, claimed responsibility for planting a pipe bomb at a community centre on the Shore Road in north Belfast.
The following night, a pipe bomb was thrown at a police vehicle at the junction of Oldpark Road and Rosapenna Street. No-one was injured in either incident.
On 18 January, postal staff at a Royal Mail sorting office in Strabane, County Tyrone intercepted a suspicious package addressed to a senior police officer.
The envelope, addressed to Chief Inspector Andy Lemon, was found to contain a small bomb.
During the first week of the new year, a number of media outlets in the Republic report that paramilitaries had publicly issued death threats against Irish people serving in the British Army.
The threats were allegedly read out in a statement on behalf of the Continuity IRA during a republican commemoration in Limerick city on 6 January. Irish police declined to comment.
An off-duty policeman found a bomb attached to the underside of his car on the Upper Newtownards Road in east Belfast.
The officer found the device during a routine check of his family car on 30 December, as he prepared to take his wife and two children out to lunch.
Police said it was "clearly intended to kill the police officer".
An Irish newspaper reported that a paramilitary plot to murder a British soldier as he returned to the Irish Republic on home leave had been foiled by Irish police.
The Irish Independent said the Continuity IRA planned to shoot the soldier when he returned to County Limerick for his Christmas holidays.
Four days before Christmas, a 27-year-old man from County Monaghan man was jailed for three years for possession of a car bomb that was left outside Crossmaglen police station in County Armagh.
The device had been loaded into a stolen car and left outside the PSNI station on 3 April, 2010, where it failed to detonate.
On the first day of the month, a prison officer was shot and killed on the M1 in County Armagh as he drove to work at Maghaberry Prison, Northern Ireland's high security jail.
David Black, 52-year-old father of two, was the first prison officer to be murdered in Northern Ireland in almost 20 years.
The killing was widely condemned by all main political parties and police said they believed dissident republicans had carried out the attack.
On 12 November, a new paramilitary group calling itself "the IRA" claimed responsibility for the murder.
The organisation is believed to have been formed during the summer of 2012, from an amalgamation of previously disparate dissident republican organisations.
In a statement issued to the Belfast-based newspaper, the Irish News, the group said it had killed him "to protect and defend" republican prisoners.
The following day, a bomb was found close to a primary school in west Belfast.
Police said the device "could have been an under-car booby trap designed to kill and maim" and added they believed dissident republicans were responsible.
Police investigate possible links to drugs and the involvement of dissident republican paramilitaries in the murder of Newtownabbey man, Danny McKay, who is shot dead at his home in the Longlands area on 25 October.
A mortar bomb is found at a house in the Ardoyne area of north Belfast on 4 October.
Thirty families are moved out of their homes for several hours after police discovered the device at the back of a house in Jamaica Street.
A 21-year-old man is later charged with preparing terrorist acts and having explosives with intent to endanger life.
On 24 October, the Home Office confirmed the threat level from dissident republicans to Great Britain had been downgraded from "substantial" to "moderate", meaning the authorities regarded an attack as possible, but not likely.
However, on the same day the Home Office said the threat level in Northern Ireland remained "severe" with an attack by dissident republicans still regarded as highly likely.
On 27 September, police in Dublin investigating dissident republican activity arrested two men after surveillance equipment was found in a hotel room overlooking a police station.
It was believed the equipment was being used to record car registration plates and identify officers involved in operations against dissident activity.
Craigavon man Ciaran Martin Collins, 35, from Drumbeg, was charged with having a semi-automatic pistol in suspicious circumstances after being arrested in a car in Lurgan.
Two other men were released pending reports to the Public Prosecution Service.
Security forces were the target of two bombs left in Londonderry on 20 September.
A pipe bomb and booby trap bomb on a timer were both made safe by the Army.
The pipe bomb was left in a holdall at Derry City Council's office grounds and the booby trap attached to a bicycle chained to railings on a walkway at the back of the offices.
Dissident republicans were blamed for leaving the bombs.
On 12 September, a 52-year-old man appeared in court charged with having guns and ammunition.
Paul McDaid, of Sheridan Street, Belfast, was arrested after police stopped and searched a car on the A1 near Hillsborough.
Leading Real IRA man Alan Ryan, 32, was shot dead in the Clongriffin area of Dublin on 3 September.
In 2000, Ryan had been jailed over the discovery of a Real IRA training camp at Stamullen, County Meath.
The Dubliner was said to be "very well known in criminal and republican circles both north and south of the border".
Three men were subsequently charged over paramilitary displays at his funeral.
Eleven republicans, including prominent Lurgan dissident Colin Duffy, were convicted of wrecking their cells at Maghaberry Prison.
Each was given a 20-month suspended sentence for causing criminal damage in the jail's Roe House wing.
On 31 August, two men appeared in court charged with firearms offences in relation to dissident republican activity in Newtownabbey.
At the start of the month, police searched the Glen Road in west Belfast after dissident republicans claimed they fired a mortar at a police vehicle.
The attack was claimed to have taken place at the same time as a gun attack on a police patrol on Friday 27 July.
Although the gun attack did take place, police found no trace of any mortar and declared their search over on 3 August.
On 26 July, some dissident republican paramilitary groups issued a statement saying they were to come together under the banner of the IRA.
The Guardian newspaper said the Real IRA had been joined by Republican Action Against Drugs (RAAD) and a coalition of independent armed republican groups and individuals.
However, police say the threat posed by dissident republicans has not been changed since the announcement was made.
A gunman fired towards police lines from within a crowd gathered at Brompton Park in Ardoyne on 12 July.
After the last of 17 shots rings out, youths clapped and cheered. No-one was injured.
Scuffles broke out after dissident republican protesters blocked the Olympic Torch's planned route near the Guildhall in Londonderry on 4 June.
It was forced to go a different way in order to reach the Peace Bridge.
Two men later appeared in court over the trouble.
Republican Action Against Drugs said it was behind a bomb attack on a police vehicle in Londonderry on 2 June.
The front of the jeep was badly damaged in what is understood to have been a pipe bomb attack in Creggan. The police described the attack as attempted murder.
Four people appeared in court on 19 May on charges linked to an alleged terrorist training camp in County Tyrone.
They were Sharon Rafferty, from Cavana Linn in Pomeroy, Sean Kelly from Duneane Crescent in Toomebridge, Terence Aidan Coney, of Malabhui Road in Omagh and Gavin Coney from Gorticashel Road, also in Omagh.
The court was told that approximately 200 rounds were heard being fired at the Formil Wood site on Gorticashel Road on 30 March, 2012.
Bullet casings had also been recovered from the area.
On 19 May three relatives of prominent Lurgan dissident republican Colin Duffy appeared in court in Lisburn charged with terrorism offences.
They were Paul John Duffy, 47, from Ailsbury Gardens, Damien Duffy, 42, from Campbell Walk, and Shane Duffy, 41, from Kilwilkie Road.
The charges included collecting information likely to be of use to terrorists, conspiracy to murder, and conspiring to cause an explosion.
A number of guns found in north Belfast on 15 May were believed to be linked to dissident republicans, police said.
They were found at Etna Drive in the Ardoyne area. Police say the find "undoubtedly thwarted attempts of these criminals to inflict death, injury and misery on the community of north Belfast".
On 30 April it emerged that five men had fled Londonderry over the course of a week after being threatened by the vigilante group, Republican Action Against Drugs.
A bomb was found under a parked car in a garage on the Ballygomartin Road in north Belfast on 28 April.
Police said "the finger of suspicion points towards dissident republican terrorists".
On 27 April police found a number of guns and ammunition during an operation at Ardglen Place in north Belfast
A pipe bomb was left under a car belonging to the elderly parents of a police officer in Londonderry on 15 April.
A number of homes were evacuated while Army bomb experts dealt with the device at Drumleck Drive in Shantallow.
The serving PSNI officer does not live in the house.
A fully primed 600lb bomb was found in a van on the Fathom Line near Newry on 26 April and made safe the following day.
A senior police officer said those who left it had a "destructive, murderous intent".
Assistant Chief Constable Alastair Finlay said it was as "big a device as we have seen for a long time".
A paramilitary-style shooting in Londonderry was deliberately timed ahead of a rally against a dissident republican group, one of its organisers has claimed.
An 18-year-old man was shot in both legs at Rinmore Drive in Creggan shortly after 22:00 BST on 26 April.
On 30 March two men were convicted of murdering police officer Constable Stephen Carroll in Craigavon in March 2009.
The 48-year-old officer was shot dead after he and colleagues responded to a 999 call.
Convicted of the murder were Brendan McConville, 40, of Glenholme Avenue, Craigavon, and John Paul Wootton, 20, of Collindale, Lurgan.
Two men arrested after an Irish police raid on a suspected dissident republican bomb factory were found guilty of possessing explosive substances on 24 February.
Conan Murphy, 25, from Dundalk, and Philip McKevitt, 58, from Aghaboys, Louth, were arrested in Dundalk in May 2010..
On 16 February police in the Irish Republic recovered a handgun and three improvised explosive devices.
The items were found near Celbridge, County Kildare, on Thursday during ongoing investigations into the activities of dissident republicans.
Londonderry man Andrew Allen was shot dead in Buncrana, County Donegal, on 9 February.
The 24-year-old father of two was shot at a house in Links View Park, Lisfannon.
Republican Action Against Drugs (RAAD) later admitted it murdered Mr Allen who had been forced to leave his home city the previous year.
On 9 February a 43-year-old Londonderry man admitted a car bomb attack at the city's Strand Road PSNI Station.
No-one was injured in the August 2010 bombing, claimed by dissident republicans Oglaigh na hEireann, but several businesses were badly damaged.
Philip O'Donnell, of Baldrick Crescent, pleaded guilty to causing an explosion likely to endanger life. He also admitted hijacking the taxi containing the 200lb device and falsely imprisoning the taxi driver.
Strabane man Martin Kelly was jailed for life by the Special Criminal Court in Dublin on 24 January for the murder of a man in County Donegal.
Andrew Burns, 27, from Strabane, was shot twice in the back in February 2008 in a church car park.
The murder was linked to the dissident republican group, Oglaigh na hEireann. Kelly, from Barrack Steet, was also sentenced to eight years in prison for possession of a firearm.
On 20 January, Brian Shivers was convicted of the murders of Sappers Patrick Azimkar and Mark Quinsey at Massereene Barracks in March 2009.
His co-accused Colin Duffy was acquitted.
Police in Londonderry believed dissident republicans were responsible for two bomb attacks on 19 January.
The bombs exploded at the tourist centre on Foyle Street and on Strand Road, close to the DHSS office, within 10 minutes of each other.
Homes and businesses in the city were evacuated and no-one was injured.
A Scottish soldier found a bomb inside his car outside his girlfriend's house in the Ligoniel area of north Belfast.
The soldier found the device while cleaning the car before going to pick up a child from school on 5 January.
It is understood the device contained a trip wire attached to the seat belt.
Police say if the bomb had gone off the soldier, and others in the vicinity, could have been killed. Dissidents admit they carried out the attack.
A 59-year-old man was charged with possession of firearms and explosives in suspicious circumstances.
He was arrested in County Fermanagh on 19 December.
Republican protesters smeared excrement on the doors and windows of the Alliance Party headquarters in south Belfast.
Earlier in the year members of the Republican Network for Unity occupied the building in support of dissident prisoners at Maghaberry.
Northern Ireland Minister Hugo Swire warned about the possibility of dissident groups using upcoming centenaries for their own purposes.
He says Stormont must take the lead to ensure those who sought to undermine the political process were not able to do so.
A masked gang tried to shoot a man at a house in north Belfast on 9 November.
Three men wearing balaclavas and armed with a handgun entered a property in Ardilea Street off the Oldpark Road.
They held a man down and attempted to shoot him, but the gun failed to go off.
Dissident republicans later said they carried out the attack.
A bomb exploded outside the City of Culture offices in Londonderry on 12 October.
A warning with a recognised codeword is understood to have been given less than an hour before the explosion in Guildhall Square.
Security sources said the attack had all the hallmarks of dissident republicans, who damaged a door of the same building with a pipe bomb in January.
The next day about 250 people took part in a rally in the city centre to protest against the attack.
Three men were arrested after a car containing a bomb was stopped on the Buncrana Road in Londonderry on Monday 26 September.
The men were remanded in custody after appearing in court later that week.
The Real IRA was blamed for two bomb attacks near Claudy, County Londonderry on 14 September.
One of the bombs exploded outside the family home of a Catholic police officer. No-one was in the house at the time.
The other device was made safe at the home of a retired doctor who works for the police.
Londonderry man Thomas Christopher Nash was jailed for seven years for hiding guns and bullets for dissident republicans.
Nash, from Iveagh Park, Prehen, Londonderry admitted having a .22 calibre hunting rifle, ammunition and a silencer with intent on 9 August 2010.
He also admitted having an imitation AK47 assault rifle and an imitation handgun with intent to cause fear of violence, and a canister of CS spray.
Paddy Dixon, a former car thief who gave information to Irish police about stolen vehicles used to transport Real IRA bombs, suffered minor injuries in a pipe bomb attack at his home in County Meath.
It is thought dissident republicans may have been behind the attack.
It is understood Mr Dixon spotted the device just before it exploded and was able to back away from the full force of the blast.
Mr Dixon had never entered the Witness Protection Programme.
He is believed to have been living quite openly in Navan.
Five men are arrested, by police investigating the murder of Constable Ronan Kerr, during a series of raids, involving 200 officers across three counties on 26 July.
Clothing, mobile phones, computers and cars were taken away for forensic analysis following the searches in Coalisland, Toomebridge, Bellaghy and Ballyronan.
The men were later released.
Prominent republican Marian Price is charged on 22 July in connection with the murders of two soldiers in Antrim in March 2009.
She was charged with providing property for the purposes of terrorism.
The charge related to the murders of Sappers Patrick Azimkar and Mark Quinsey at Massereene barracks.
A mortar bomb and a quantity of cigarettes were uncovered during an arrest and search operation in the Etna Drive-Jamaica Street area of Ardoyne in north Belfast.
Seventy families were moved from their homes during the security operation on 21 July.
Irish police said they believed bomb components found in County Louth on 25 June were to be used for a device in Northern Ireland.
The Irish army carried out a controlled explosion at a site in Hackballscross.
Police described the find as significant and linked it to the dissident group Oglaigh na hEireann.
Police said they believed dissident republicans were responsible after a photographer was shot during violence on 21 June in east Belfast.
It happened during a second night of trouble at a sectarian flashpoint on the Lower Newtownards Road.
Police said the trouble was orchestrated by the loyalist paramilitary group, the UVF.
A pipe bomb exploded after being thrown into a house in Muff, County Donegal.
A man who was inside was not injured. Dissident republicans are suspected of being involved.
Two masked men throw a holdall containing a bomb into a Santander bank branch in Londonderry's Diamond just after midday on Saturday 21 May.
Police cleared the area and the bomb exploded an hour later. No-one was injured.
However, significant damage was caused inside the building.
A grenade was thrown at police officers during a security alert at Southway in Londonderry on 9 May.
The device, which was described as "viable", failed to explode.
Two children were talking to the officers when the grenade was thrown.
The mother of one of them said he could have been killed and whoever threw the grenade must have seen the children.
On 30 April, Michael Patrick Finbar Johnston, 28, from New Lodge Road, in north Belfast, is charged with having articles for the purpose of terrorism and of preparing for acts of terrorism.
He was arrested over the seizure of four bomb timers, a find that police linked to dissident republican activity.
Three men are charged on 25 April with possession of firearms, preparation for committing acts of terrorism and possession of articles likely to be of use to terrorists.
It follows the discovery of what police described as a "substantial amount" of machine guns and rifles in a vehicle in Keady, south Armagh.
More weapons were found in separate follow-up searches in south Armagh and east Tyrone.
Among them were Semtex explosives, a horizontal mortar, 25 kilos of homemade explosives, an automatic weapon, a silencer, ammunition, three timer power units, booster tubes and a detonator.
The dissident republican group, the Real IRA, threatened to kill more police officers and declared its opposition to the Queen's first visit to the Irish Republic.
A statement was read out by a masked man at a rally organised by the 32 County Sovereignty Movement in Londonderry on Easter Monday, 25 April.
A 500lb bomb was left in a van at an underpass on the main Belfast to Dublin Road in Newry.
The alert began on the night of Thursday 7 April and was cleared on Saturday 9 April. Several motorists drove past the vehicle on the Friday.
Constable Ronan Kerr was killed after a bomb exploded under his car outside his home in Omagh, County Tyrone, on 2 April.
No group claimed responsibility for the attack but dissident republicans were blamed.
The 25-year-old had joined the police in May 2010 and had been working in the community for five months.
Northern Ireland Chief Constable Matt Baggott described Constable Kerr as a "modern-day hero".
The PSNI described a bomb left near Londonderry courthouse as a "substantial viable device".
District Commander, Stephen Martin, said a beer keg, left in a stolen car, contained around 50kg of home-made explosives.
The alert started on the evening of Sunday 27 March.
Irish police investigated possible dissident republican involvement in the shooting of three people in a park in Blanchardstown, Dublin on Sunday 27 March.
Two of the injured men were shot in the body, the other in the head.
A number of shots were fired at police officers at Glen Road in Londonderry on the night of 2 March.
Police said it was an attempt to kill.
On 18 February Sinn Fein condemned a threat they said had been made by dissident republicans against the brother of Pat Finucane as "beyond contempt".
Gerry Kelly said the threat against community worker Seamus Finucane came from the dissident republican group, Oglaigh na hEireann (ONH).
Irish police investigating the activities of dissident republicans discovered items they said could be used to make explosive devices.
They were found during a search of a house in Barnstown in County Wexford.
On 30 January two men arrested in Galway after police found guns and explosives were charged at a court in Dublin.
They were charged with unlawful possession of an explosive substance, unlawful possession of a revolver and unlawful possession of ammunition.
The PSNI confirmed two bombs were found in a security alert that started on the Antrim Road in north Belfast on 23 January and lasted several days.
The second viable device was found behind a scout hall while the first found, an "anti-personnel device", was found outside a shop.
On 22 January, the leader of the Irish Republic's main opposition party, Enda Kenny of Fine Gael, told the Alliance Party conference, if he was the country's prime minister, he would do everything within his powers to combat the threat of dissident republicans.
Police in the Republic of Ireland questioned five men arrested in connection with the discovery of a "bomb factory" on a farm in County Kildare.
A 22-year-old man appeared in court on 12 January in connection with a dissident republican bomb attack on a police station in Londonderry.
A policeman found an unexploded grenade outside his home in County Fermanagh.
The device was discovered at the property in Drumreer Road, Maguiresbridge, on 23 December.
A terrorism charge against 40-year-old dissident republican Gary Donnelly from Londonderry was withdrawn on 22 December.
In the Republic, three men from Northern Ireland were jailed for IRA membership on 15 December.
Gerard McGarrigle, 46, from Mount Carmel Heights in Strabane was sentenced to five years in prison.
Desmond Donnelly, 58, from Drumall, Lisnarick, Fermanagh and Jim Murphy, 63, from Floraville in Enniskillen, were given three years and nine months.
They were arrested in Letterkenny in February after Irish police received a tip-off that dissident republicans were about to carry out a 'tiger' kidnapping.
On 10 December, the Police Federation claimed the level of dissident republican terrorist activity in Northern Ireland was being played down by the police and government to make NI appear more normal than it actually is.
A 21-year-old woman was charged with having a gun and ammunition with intent to endanger life on 5 December.
The arrest followed a search in west Belfast by detectives investigating suspected dissident republican activity.
Four men were arrested after an explosive device was found in a car near Dundalk, County Louth on 1 December.
The device, described by police as a viable mortar, was made safe by bomb disposal experts.
A meeting of the Derry DPP in the Guildhall on 25 November had to be abandoned after republican protesters blew horns and chanted slogans.
A military hand grenade was used to attack police officers called to a robbery at Shaw's Road in west Belfast on 5 November.
Three police officers were hurt and one of them suffered seri ous arm injuries when the grenade was thrown by a cyclist who then made off.
The dissident paramilitary group Oglaigh na hEireann (ONH) said it was responsible for the attack.
Two men were shot in the legs in attacks in Londonderry in the space of 48 hours - the first on Sunday 17 October, the second on Tuesday 19 October.
A general purpose machine-gun and improvised mortar bomb were among the weapons found in a police search in a wooded area at Togher, Dunleer, County Louth on 11 October.
Ten people were arrested after Irish police found weapons and bomb making material in raids in Counties Louth, Wexford and Waterford on 8 October.
Two men later appeared in court while files were prepared for the DPP on the others.
A car bomb exploded close to the Ulster Bank, shops and a hotel on Londonderry's Culmore Road on 4 October.
The area had been cleared when the bomb exploded, but the blast was so strong that a police officer who was standing close to the cordon was knocked off his feet.
Masonry and glass from smashed windows were strewn across the Culmore Road.
Lurgan man Paul McCaugherty was jailed for 20 years for a dissident republican gun smuggling plot that was uncovered after an MI5 sting operation.
McCaugherty was found guilty of attempting to import weapons and explosives.
Dermot Declan Gregory from Crossmaglen, was found guilty of making a Portuguese property available for the purpose of terrorism. He was sentenced to four years.
A 54-year-old Newry man was charged with seven offences including possession of firearms and ammunition with intent in the preparation of acts of terrorism after police discovered firearms including a "walking stick which could be turned into a gun" in the shed of a house.
On 24 September, Home Secretary Theresa May said an attack on Britain by "Irish-related" terrorists is a "strong possibility".
She was speaking as MI5 raised the country's threat level.
The British and Irish governments again insisted they are not holding talks with the dissidents.
The head of MI5 told a meeting of security professionals in London that the threat from dissident republicans is rising.
Jonathan Evans said MI5 could not rule out the possibility of dissidents extending their attacks to Great Britain.
Three children suffer minor injuries when a bomb exploded in a bin in Lurgan's North Street on 14 August.
The bomb went off at a junction where police would have been expected to put up a cordon around the school. The explosion injured the children after it blew a hole in a metal fence.
Three other alerts in the town were declared elaborate hoaxes.
Chief Inspector Sam Cordner said the attack had "stark similarities" to the 1998 Omagh atrocity.
Deputy First Minister Martin McGuinness told the BBC the British government has talked to dissident republicans in recent weeks,
He also said the Irish government had been meeting with dissidents for years.
A booby trap partially exploded under the car of a former policeman in Cookstown, County Tyrone, on 10 August.
The man was unhurt in the attack, but it is the first time one of the latest series of booby-trap bombs detonates.
A bomb is found under the car of a Catholic policewoman in Kilkeel in County Down on 8 August.
It is believed the device fell off the car before being spotted by the officer.
Irish police investigating dissident republican activity arrest five men in County Louth on the same day.
Guns, ammunition and balaclavas are found in two cars during the operation.
On 4 August, booby trap bomb was found under a soldier's car in Bangor.
It was thought the device could have been planted by dissident republicans close to the base where he was stationed and he drove home without it being detected.
It then fell off and he discovered it as he was about to leave his home.
A car that exploded outside a police station in Londonderry contained 200lb of homemade explosives.
No-one was injured in the attack, which happened on 3 August, but several businesses were badly damaged in the blast.
On 28 July, an 18-year-old man was abducted in west Belfast and driven two miles away to the Lenadoon estate where he was shot in both legs.
Police said a shooting at a house in Londonderry on 26 July could be linked to the vigilante group Republican Action Against Drugs.
Three men and a woman were in the property at Dunmore Gardens when four masked men forced their way in and fired two shots.
Four men and a teenage boy were arrested on the Falls Road in west Belfast following an attempted paramilitary shooting at a house in the St James' area.
The five were later charged with terrorism offences.
The remains of an exploded pipe bomb were found in the grounds of a west Belfast police station on 22 July.
The device was discovered at Woodbourne PSNI station on the Stewartstown Road.
A bomb exploded between Belleeks and Cullyhanna in south Armagh, blowing a crater in the road and damaging a stone bridge on 10 July.
Police viewed it as an attempt to lure them into the area in order to carry out a follow-up ambush.
Dissident republicans were blamed for organising two nights of sustained rioting in the Broadway and Bog Meadows areas of west Belfast on Friday 2 and Saturday 3 July.
Later rioting on 11, 12, 13 and 14 July in south and north Belfast, Lurgan and Londonderry is also believed to have involved dissidents.
Scores of police officers were injured during the violence, which featured gun attacks, petrol bombs and other missiles being thrown.
Five men were arrested after police stopped three cars near Omeath in County Louth on 10 July.
Irish police suspected they were trying to move explosives across the border.
One man was charged, while four others were released while a file was prepared for the DPP.
Shots are fired at Crossmaglen PSNI station on 2 July.
Dissident republicans said they were behind two similar attacks in December and January.
On 30 June, two men were convicted of attempting to import weapons and explosives for use by dissident republicans.
Paul McCaugherty, 43, of Beech Court in Lurgan and Dermot Declan Gregory of Concession Road in Crossmaglen, were caught in an MI5 sting operation.
A Belfast court heard McCaugherty handled over bundles of euros in a specially adapted bag to an undercover agent, saying he needed "explosives, pistols, AK-47s, armour-piercing stuff, snipers, cords and detonators".
A report by the Independent Monitoring Commission on 26 May said dissidents "remain highly active and dangerous".
It said the threat was "very serious" but they were not able to mount a campaign like the Provisional IRA.
Two men were charged with explosives offences after the discovery of an alleged dissident bomb-making factory near Dundalk on 22 May.
Irish Justice Minister Dermot Ahern said the find foiled an attack in Northern Ireland.
A car bomb exploded outside Newtownhamilton Police Station in County Armagh, injuring two people.
Local residents also reported hearing gunshots before the blast.
Police chiefs said the threat from dissident republicans was higher than at any time since the Omagh bomb almost 12 years previously.
Senior police officers believed rival factions in the Real IRA and Continuity IRA have increased co-operation and stepped up recruitment.
There were five pipe bomb attacks on houses in the west of Northern Ireland in a week - two of them claimed by a group calling itself Republican Action Against Drugs.
A car bomb was defused outside Newtownhamilton police station in south Armagh on Tuesday 13 April.
A bomb in a hijacked taxi exploded outside Palace Barracks in Holywood, on Monday 12 April - the day policing and justice powers were transferred to Northern Ireland.
One man suffers minor injuries.
A two-day protest by dissident republicans at Maghaberry Prison ended on Easter Tuesday. The prisoners had barricaded themselves into a dining room.
Police say a car bomb left outside Crossmaglen on Easter Saturday night could have killed or seriously injured anyone in the area. The bomb - made up of a number of flammable containers - was made safe by Army experts.
On 12 April, the Real IRA leaves a no-warning car bomb outside MI5's Northern Ireland headquarters at Palace Barracks in Holywood, County Down.
The blast is timed for the same day that policing and justice powers are devolved from Westminster to Stormont. An elderly man walking near the Army base at the time of the explosion is treated in hospital for minor injuries, but the bomb causes little damage.
Dissidents were blamed for a series of alerts in Belfast, Londonderry and on the railway line in south Armagh, which caused major traffic disruption on 19 March.
Shots were fired at police as they investigated the railway alert, although no-one was injured.
The naked and bound body of 31-year-old Kieran Doherty was found close to the Irish border near Derry on 24 February.
The Real IRA said it killed Mr Doherty who, it claimed, was one of its members.
Two days earlier a bomb damaged the gates of Newry courthouse in County Down.
Officers were evacuating the area when the bomb went off. Police said it was a miracle no-one was killed.
February had begun with Irish police stopping a suspected attack by dissident republicans in County Donegal.
A car was stopped at Cooladawson, near Stranorlar, and a man arrested but three other men who were in the vehicle ran off across fields.
In Belfast, 40 families were moved from their homes after a pipe bomb was thrown at a police station.
Dissidents were also suspected of being involved in organising rioting in Craigavon in County Armagh at the end of the month.
In Cork, cash, drugs and a number of suspected imitation guns were seized during a major operation targeting dissident republican paramilitaries.
The operation followed a claim from the Real IRA that it shot dead a convicted drug dealer in Cork on 20 January.
There was widespread condemnation in Londonderry over a campaign by the 32 County Sovereignty Movement.
The group, regarded as the Real IRA's political wing, said it would picket shops that deal with the police in protest at stop and search tactics.
A 33-year-old Catholic police officer was seriously injured in a dissident republican car bomb about a mile from his home in Randalstown in County Antrim.
A PSNI spokesman said it was too early to say which group was behind the attack.
The family of a Londonderry shopkeeper who sells smoking paraphernalia and "legal highs" said they believe he was shot and injured by dissident republicans on 27 January because of his business.
On the last day of the month the Real IRA opened fire on a police station in County Armagh.
No-one was injured in the attack in Bessbrook, but Ulster Unionist MLA Danny Kennedy said he condemned "this act of wanton intent and murder".
Shots were fired at Crossmaglen Police Station on 30 December. No-one was injured.
The body set up to monitor paramilitary activity in Northern Ireland said dissident republicans were more active than at any time in the past four-and-a-half years.
The Independent Monitoring Commission published its 20th report, which said dissidents were directing their efforts to kill PSNI officers.
Dissident republicans were also blamed for leaving a car containing a 400lb (181kg) bomb outside the Policing Board's headquarters in Belfast.
The car, which had been driven through a barrier by two men who then ran off, burst into flames when the device partially exploded.
On the same night, shots were fired during an undercover police operation in the County Fermanagh village of Garrison, in what police described as an attempt to kill a trainee PSNI officer.
Five men were arrested by police on both sides of the border.
Two of the men, a former Irish army reservist and an unsuccessful council election candidate, were later charged with attempted murder.
One of Northern Ireland's highest profile judges moved out of his Belfast home over fears of a dissident republican threat against him.
Mr Justice Treacy's £650,000 house was bought under the Housing Executive's Special Purchase of Evacuated Dwellings (Sped) scheme.
Four men dressed in paramilitary style uniform and black masks fired a volley of shots over the coffin of a dissident republican who died in a Londonderry police station.
It was believed that John Brady had taken his own life at Strand Road station days earlier.
The dissident republican vigilante group, Republican Action Against Drugs (RAAD) claimed responsibility for shooting and injuring a 27-year-old man in Londonderry.
One of the police officers who went to the scene of the gun attack was knocked unconscious after he was hit on the head with a lump of concrete.
The DUP's Ian Paisley Jr said police had warned him that dissident republicans were planning to murder him.
Mr Paisley, who was then a member of the Policing Board, said officers contacted him to inform him of the foiled attack.
A police officer's partner was injured when a bomb exploded under her car in east Belfast.
The 38-year-old was reversing the vehicle out of the driveway of a house when the device exploded.
In the same month a bomb exploded inside a Territorial Army base in north Belfast.
The police confirmed that "some blast damage" had occurred inside the base off the Antrim Road and shrapnel from the overnight explosion was found in neighbouring streets.
The PSNI said a 600lb (272kg) bomb left near the Irish border in south Armagh was intended to kill its officers.
The bomb was defused by the Army near the village of Forkhill.
Days later the Real IRA claimed responsibility for placing two explosive devices near the homes of a policeman's relatives in Londonderry.
The first device exploded outside his parents' home while a second device, which was found outside his sister's home, was taken away for examination by the Army.
A group of armed and masked men, believed to be from a faction of the Real IRA, set up a roadblock in the south Armagh village of Meigh.
They handed out leaflets warning people against co-operating with the security forces on either side of the border.
Sinn Féin blamed the Real IRA for orchestrating rioting in north Belfast. At least one shot was fired at police and two blast bombs were thrown.
Dissident republican protesters disrupted a meeting of the District Policing Partnership in Londonderry.
Conor Murphy, then a Sinn Féin MP and minister in Northern Ireland's devolved administration, blamed dissident republicans for an arson attack on his home in south Armagh.
Dissident republicans were suspected of involvement in a petrol bomb attack on the Londonderry home of senior Sinn Féin member Mitchel McLaughlin.
The Real IRA in Londonderry said it shot a convicted rapist in the legs, one of a series of such attacks in the city at the time.
Northern Ireland's then Deputy First Minister Martin McGuinness said dissident republicans had threatened to kill him.
Two young soldiers were shot dead as they collected pizzas outside Massereene Barracks in County Antrim.
Sappers Patrick Azimkar and Mark Quinsey were killed just hours before they were due to be deployed to Afghanistan.
The Real IRA is blamed for the attack.
Within 48 hours a policeman Stephen Carroll was shot dead in Craigavon, County Armagh, becoming the first police officer to be murdered in Northern Ireland since 1998.