Belfast, Northern Ireland (CNN) -- Belfast was calm early Wednesday morning, a day after scores of youths clashed with police in an expression of rage over a parade in the Ardoyne area of north Belfast.
The clashes Tuesday night was the second consecutive night of unrest in the city.
Nationalist youths threw stones, gasoline bombs, golf balls and fireworks at police following the Orange Order Protestant parade -- held on a date often marked by sectarian violence, the Twelfth of July.
After the march passed, the rioters grew in number and ferocity and police responded with plastic bullets and water cannon. Outbreaks of violence also ignited in east and south Belfast, Londonderry and other parts of Northern Ireland.
Police said "calm had been restored" in Belfast by 2 a.m. Wednesday.
Trouble had continued for a time in Londonderry, also known as Derry, where police said 13 arrests were made, including 12 men and one woman. Earlier, they said a 14-year-old juvenile had been arrested in Derry and a crate of petrol bombs recovered.
A police spokesman also said five arrests - three juveniles and two adult males - had been made in south Belfast. Two cars were set on fire there and "a member of the public was injured when masonry was thrown," said police.
CNN witnessed a number of police officers being struck with missiles and set on fire by gasoline bombs during the violence in Ardoyne - and a press photographer suffered a leg wound when he was hit by a plastic bullet fired by police. A number of vehicles were hijacked and burnt out during the disturbances.
Police had appealed for calm on Tuesday.
"Whilst I commend the bravery and leadership of many within the community who worked tirelessly to reduce the disorder and calm tensions -- we need everyone to keep working to build and maintain calm across all local areas," Assistant Chief Constable Alistair Finlay said in a statement.
He said a number of officers were injured during the disorder.
"We have unfortunately witnessed firsthand this evening how violence damages people's homes and businesses, it sets back relationships and leaves wounds which take time to heal," Finlay said. "It is not representative in any way of the vast majority of people here who want to get on with their lives."
Tuesday's incidents came a day after at least 22 officers were injured amid similar attacks elsewhere in Belfast.
On Monday night, police fired more than 50 plastic bullets and used a water cannon to disperse rioters, who threw more than 40 gasoline bombs, the Police Service of Northern Ireland said. A number of arrests were made, police added, without specifying how many.
Monday's violence was centered in Catholic areas of Belfast ahead of the main day of the Protestant marching season, when loyalists parade through the streets.
A police spokeswoman said the trouble started late Monday and continued into Tuesday. The most serious disorder was in the Broadway area of west Belfast and involved 100 to 200 people.
Police were investigating reports that gunshots were fired during the disturbances.
Police said several vehicles were hijacked and set on fire in the area, while crowds attacked officers with missiles "including masonry and petrol bombs."
At one point, a bus was hijacked and driven toward police lines but crashed a short distance away.
The province suffered decades of violence known locally as the Troubles, in which more than 3,500 people were killed before a 1998 peace accord known as the Good Friday Agreement.
The Troubles pitted mostly Catholic republicans, who want the province to become part of the Republic of Ireland, against pro-British loyalists, who are mostly Protestant.
This year has been one of the most violent since the Good Friday Agreement.