The bomb that devastated Omagh town centre in August 1998 was the biggest single atrocity in the history of the Troubles in Northern Ireland.
Twenty-nine people were killed, including nine children, a woman pregnant with twins and three generations of one family.
It came less than three months after the people of Northern Ireland had voted yes to the Good Friday Agreement.
Dissident group the Real IRA claimed responsibility for the attack.
In June 2009, four men were held responsible for it in a civil case brought by the families of those killed.
BBC News NI remembers those who lost their lives in the attack 20 years ago.
Spaniard Rocio Abad Ramos, 23, from Madrid was supervising a Spanish-Irish language exchange programme with Buncrana Primary School in County Donegal in the summer of 1998.
She and the students had been shopping in Omagh as part of an outing when she was killed by the bomb.
She had been due to return to Spain for her sister's wedding and was just a month away from finishing her biology degree.
James Barker was described as a "happy boy with an infectious smile" - he was a 12-year-old student at Buncrana Primary School and was also killed while on a school trip.
His mother Donna Maria Barker relocated to England 18 months after the explosion and James's body was then reburied at his former English school in Weybridge in Surrey.
She said she "never realised how green his eyes were" until she had to identify his body, adding: "That image will stay with me for the rest of my life."
Another of those who was on the Buncrana Primary School language exchange trip, Fernando Blasco Baselga was a 12-year-old boy from Madrid.
His father Manuel, who had been hurt in a terrorist bomb attack in Madrid in six years earlier, identified Fernando's body at a temporary mortuary at Omagh army barracks.
Fernando's sister Donna Marie was also a student on the excursion and suffered serious facial injuries in the explosion.
Geraldine Breslin was a 43-year-old married mother who worked as a shop assistant at Watterson's drapers.
Eyewitnesses said they saw her calling out for her husband in the aftermath of the attack in spite of her serious injuries.
She died eight hours after the blast - at the inquest into the deaths the coroner said she had been "fighting very much to live".
Working in a beauty salon on the day of the explosion, Deborah-Anne Cartwright was due to start a textile design degree in Manchester a month later.
She had been involved in cross-community work while she was at school and had been to Denmark as part of a student exchange scheme.
The 20-year-old was moved out of the premises she was in when the bomb warning was issued and she walked down Market Street where the bomb detonated.
Gareth Conway was an 18-year-old student who had just gained a place on an engineering course at university when he was killed.
His sister was a nurse at the Tyrone County Hospital and went to work after hearing about the bomb - it was then that she heard he was missing.
Gareth's school friends and Gaelic football teammates formed a guard of honour at his funeral.
Toddler Breda Devine was killed in the blast while out with her mother.
Tracey Devine was only able to grieve for her 20-month-old daughter after she came out a two-month coma caused by the blast.
Breda, the second-youngest victim of the bomb, was due to be the flower girl at the wedding of her uncle and his fiancée.
Eight-year-old Oran Doherty was also a student at Buncrana Primary School and was killed alongside friends James Barker and Sean McLaughlin.
He had been looking forward to the trip to Omagh and his sister gave him sweets for the journey because had was a bad traveller, she said.
Oran was a keen Celtic fan and was buried wearing the club jersey.
Self-employed mechanic Aidan Gallagher was killed in the blast while shopping with a friend in Omagh for boots and jeans.
His father Michael treasured his last memory of Aidan: "It was just lovely to remember those last few minutes that he was standing there, just the way you would want him to be."
Michael subsequently became the chairman of the Omagh Self Help and Support Group for victims of the attack and relatives of those who were killed and injured.
Esther Gibson was a Sunday school teacher who was shopping in Omagh when she died.
The 36-year-old had been preparing for her wedding, which was due to take place the following summer, and she and her fiancé Kenneth had their engagement portrait taken in the town that day.
After her death Kenneth said: "When they killed her I died with her."
Mary Grimes was celebrating her 66th birthday when she was killed alongside her daughter Avril and granddaughter Maura.
The mother of 12 had been taken shopping by Avril; her husband had bought flowers to welcome her home later that day.
The last loaf of bread that she baked was placed on the altar for her funeral.
Olive Hawkes, 60, was a married mother of two who was killed while doing her regular Saturday shopping in Omagh.
She was a Methodist church treasurer for 20 years and was said to be highly regarded in both unionist and nationalist communities.
She had been due to celebrate her ruby wedding anniversary just days after the bombing.
A student at Dundee University, Julia Hughes was working in a photography shop in Omagh for the summer.
She was planning to return to Scotland the next month to complete the final year of her accountancy degree.
At her funeral, her father said there was "absolutely no answer on this side of eternity" as to why his 21-year-old daughter died.
Seventeen-year-old Brenda Logue was with her mother and grandmother on the day of the attack and left the SD Kells clothing shop to see what was happening outside.
She played Gaelic football and was a pupil at high school in Carrickmore in County Tyrone.
Her exam results arrived two days after her death - she had been planning to study leisure and tourism at college.
Another 17-year-old girl, Jolene Marlow was killed while in Omagh with her sister and her great aunt.
A talented Gaelic footballer, her team had won the Tyrone county championship 10 days earlier.
She was buried on the day that her A-level results came out, confirming her university place to study physiotherapy.
Ann McCombe, 48, was another shop assistant at Watterson's drapers in Omagh.
She was killed while she was on a tea break with her colleague Geraldine Breslin.
Her husband, who was in Scotland with their son on the day of the bombing, said that when he heard about it he "knew in my heart" Ann was severely injured or dead.
Brian McCrory was in the town to buy paint to redecorate his home when he was caught up in the blast.
His son had helped at the hospital after the bombing, unaware that Brian was among the dead.
Police had to take fingerprints from a crane at the family's business in order to identify the 54 year old's body.
Seventeen-year-old Samantha McFarland was killed alongside her best friend Lorraine whilst working as a voluntary shop assistant for the charity Oxfam.
She was a former pupil at Omagh High School and was studying for her A-levels at Strabane College.
Her mother took on her voluntary work at the Oxfam shop after her death as a tribute to her.
Three weeks after the explosion, Sean McGrath died of his wounds in the Royal Victoria Hospital in Belfast.
He had been caught up in the blast that happened on the same street that he was born on 61 years earlier.
The retired baker and married father of four was described by one friend as "one of the loveliest men ever to walk the streets of Omagh".
Sean McLaughlin, another boy of 12 years of age, was a pupil at Buncrana Primary School.
He was a Manchester United supporter and an altar boy at a church in Buncrana.
He lived close to his friend Oran Doherty, who also died in the blast.
Pregnant with twins when she was killed by the explosion, Avril Monaghan, 30, lost her life alongside her mother Mary and daughter Maura.
She had four children under seven years of age and her twins were due to be born two months later.
Some of her 10 brothers carried her coffin at her funeral.
The youngest victim of the Omagh bomb was 18-month-old Maura Monaghan.
She was the third generation of her family - her grandmother and mother included - to be killed in the attack.
Her small white coffin was carried by relatives at the funeral service she shared with her mother Avril.
A pupil at Omagh High School, Alan Radford had been in the town to help his mother to do her weekly shopping.
He was due to start training as a chef the following month.
His brother Paul spent time helping some of the bomb victims at the hospital, oblivious to the fact the 16-year-old had been killed.
Elizabeth Rush, a mother of three, owned a shop with a cafe upstairs in Omagh and she died while she was serving customers.
The 57 year old was described by her parish priest as "a caring person, always friendly".
She and her husband Laurence had married as teenagers and after her death he condemned the perpetrators of the attack: "They haven't just destroyed my wife, they have destroyed my life."
Just hours before the going to work in Omagh Veda Short saw her grandson Lee, who had been born that day.
Veda, 56, was a shop assistant in Watterson's drapers and was on her lunch break when the bomb went off.
The mother-of-four was one of three of the shop's staff who were killed by the blast.
Described as a home bird by her husband Kevin, Philomena Skelton only visited Omagh twice a year - once in summer and once at Christmas - and was in the town to buy school uniforms.
Kevin was in the shop next to her at the moment the bomb exploded and her daughters, Paula, Tracey and Shauna were injured in the explosion.
He found Philomena, 39, in the rubble after the blast: "I reached for her arm to find her pulse and I could find nothing - I knew she was dead."
Bryan White was last seen alive with his father Fred leaving the Salad Bowl, a fruit and vegetable shop on Market Street.
The 27-year-old was a qualified horticulturist and was due to start a new job the following week.
Like his father he was a member of the Orange Order and he also served as an officer in the Boys Brigade, a Christian youth organisation.
Fred White was shopping in Omagh with his son Bryan at the time of the attack.
He was a treasurer in the Omagh Ulster Unionist Association and played a part in the successful campaign that led to the election of William Thompson as the West Tyrone MP the previous year.
The 65 year old was survived by his wife Edith and he and his son were buried side by side.
Schoolgirl Lorraine Wilson was 15 when she when was killed alongside her best friend Samantha McFarland - they had been working in the town's Oxfam shop.
She had hopes of becoming an air hostess.
Her coffin was draped with pink and white flowers as it was carried into the family's church.