A second night of rioting broke out in Northern Ireland at the height of the Protestant marching season, with police officers attacked and numerous people arrested, police said Wednesday. Petrol bombs, bricks, bottles and fireworks were thrown at officers and cars were set alight in the Ardoyne area of north Belfast, and riot police responded by firing baton rounds and water cannons. Police said some officers were briefly set on fire when they were hit by petrol bombs. 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. Three young people and two adult men were arrested, police said. Seven men were arrested as disorder also broke out in the city of Derry. Thousands of members of the Protestant Orange orders 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 loyal orders began lighting bonfires, the signal for the start of the Twelfth. However, Assistant Chief Constable Alistair Finlay, speaking on Monday, said the vast majority of parades across Northern Ireland passed off peacefully. He condemned the \"pockets\" of disorder as \"totally unacceptable\".