A second night of rioting erupted in Northern Ireland at the height of the Protestant marching season, with two police officers briefly set on fire by petrol bombs and numerous arrests, police said Wednesday.

Rioters threw petrol bombs, bricks, bottles and fireworks at officers and set cars alight in the Ardoyne area of north Belfast. Riot police fire baton rounds and water cannons in response.

There was also trouble in south Belfast, where two parked cars were set on fire and a member of the public was hit by thrown masonry, and in the city of Londonderry.

Police made nine arrests in the Ardoyne, 13 in Londonderry and five on the border of south and east Belfast, police said.

Alistair Finlay, Assistant Chief Constable of the Northern Ireland Police Service, said it was "hugely regrettable that we come to this situation each year."

"We must ensure we are not sending out the wrong messages about small pockets of Northern Ireland," he told reporters in Belfast, adding that "violence and mayhem is not wanted here."

Finlay did not confirm whether any dissident organisation was responsible for the riots.

The rioting followed a nationalist protest march held to coincide with marches by the Protestant Orange orders, which walk the streets every July 12 to commemorate the 1690 Battle of the Boyne victory of the Protestant king William III of Orange over the Catholic king James II.

There are often clashes as they pass through Catholic, nationalist areas.

Twenty-two police officers were injured in rioting in Belfast on Monday night when the loyalist orders began lighting bonfires, the signal for the start of the Twelfth.

Finlay, speaking on Monday, said the vast majority of parades across Northern Ireland passed off peacefully. He condemned the disorder as "totally unacceptable".