A police chief has said overnight violence in nationalist areas of Northern Ireland after 12 July parades was "totally unacceptable".
A policewoman suffered head injuries when she was hit by a lump of masonry in riots at Ardoyne in Belfast.
In Londonderry, youths in the Bogside set a police car alight with petrol bombs and a gunman fired five shots at it. No-one was injured.
There was sporadic violence in parts of Belfast, Derry and Lurgan.
Assistant Chief Constable Alistair Finlay said the past 24 hours had been "a very challenging time for policing".
Seventy baton rounds were fired by police and 55 officers were injured on Monday night.
Over two days of violence, police said 82 officers had been hurt.
In Ardoyne, north Belfast, on Monday evening, police fired a number of baton rounds after being attacked.
Two people injured by baton rounds were treated at the Royal Victoria Hospital in Belfast. They were later discharged.
More than 100 riot police were involved in an operation to remove nationalist protesters blocking the road ahead of the return of an Orange Order march.
The crowd threw petrol bombs, a blast bomb and other missiles at police. The policewoman was struck on the head by debris thrown from the roof of the shops at about 2200 BST.
Police said they had to protect their injured colleague and ambulance crews from further missiles in Ardoyne as they tended to her, before she was taken to hospital.
Her condition is described as stable but "not serious".
The parade eventually went past the flashpoint area at Ardoyne shops. As it passed, stones and bottles were thrown.
The march had been delayed for about 90 minutes because of the protests.
The rioting in north Belfast continued for several hours. At one point, rioters used a green laser pen to try and blind police officers.
There was rioting in Derry at about 0110 BST on Tuesday morning at Lecky Road in the Bogside.
Petrol bombs were thrown at a police patrol car which was on fire when a gunman appeared from behind a pub and fired five shots at the vehicle from a handgun before disappearing.
No-one was injured and the gunman ran off.
Sporadic trouble broke out in other parts of Northern Ireland as Protestant Orangemen staged their annual parades.
On the eve of the marches, three police officers were shot during rioting.
The Twelfth of July is the annual high-point of the loyal orders' parading calendar.
Some marches have been a source of tension between nationalists who see the parades as triumphalist and intimidating, and Orangemen who believe it is their right to walk on public roads.
On the Ormeau Road bridge in south Belfast, petrol bombs and paint were thrown at police on Monday evening.
A car was later set alight on the bridge.
Police also dealt with minor disturbances on the Albertbridge Road and Short Strand area in the east of the city.
Police in riot gear responded to what a PSNI spokesperson described as "a major disturbance" at Botanic train station in south Belfast.
Dozens of police officers moved into the area after a disturbance on the platform.
A PSNI spokesman said two men and a woman would be reported to the Public Prosecution Service for alleged disorderly behaviour and assault on the police.
In west Belfast on Monday afternoon, a bus driver was forced to drive to a police station by two masked men who claimed they had left a bomb on the upper deck.
It is understood the men boarded the bus at Glencolin Walk shortly before 1600 BST.
He drove the bus to Woodbourne police station. Police later said the alert was a hoax.
In the north of the city, a number of cars were hijacked in the Oldpark Road area.
In Lurgan, County Armagh, youths halted a train in the Lake Street area at about 1630 BST and attempted to set it on fire, but the driver managed to restart the vehicle.
None of the 55 passengers on board the Belfast to Dublin are believed to have been injured.
A van was also hijacked in the area.
Later, police said there was sporadic violence in the town's Antrim Road area, with petrol bombs being thrown at officers.
In Armagh city, a vehicle was set on fire on the Killylea Road and a large number of youths gathered.