Roman Catholic hard-liners assaulted police and Protestant marchers in a religiously polarized part of Belfast (search), and nearly 30 people were injured, Northern Ireland police said Saturday.

Friday night's violence flared as a parade by Protestants of the Orange Order (search) brotherhood passed a crowd of hostile Catholics on the edge of the Ardoyne district. Hundreds of police in riot gear kept the two sides apart, but Catholic men and youths spent more than an hour hurling bottles, bricks and at least 10 gasoline bombs at the police lines.

The Police Service of Northern Ireland (search) said 18 officers were injured, but none seriously. The 11 injured civilians included a 14-year-old girl with a broken arm.

The rioting fizzled out once police deployed mobile water cannons to douse the Catholic crowd.

"We were deployed in sufficient force to prevent a bad situation from getting worse, but as it was, our officers came under sustained attack," said Superintendent Gary White, who commanded the police operation.

Police said they arrested three people for rioting and planned more arrests once people caught on surveillance camera footage could be formally identified.

Several hours later, in apparent retaliation, Protestant militants attacked five homes in the nearby Ligoniel district. All were struck at about 2:30 a.m. Saturday with paint-filled balloons. Three also suffered broken windows or scorch damage from ignited gasoline-filled bottles.

Ardoyne is one of the most hard-line Catholic districts of north Belfast. Residents there generally loathe the Orange Order, an anti-Catholic fraternity group that mounts more than 2,000 parades annually, mostly in July.

Several Orange Order parades scheduled for next month are expected to face organized Catholic opposition. The confrontations — almost always with police in the middle — have frequently caused widespread street violence, particularly from 1996 to 1998.

Catholics led by Sinn Fein, the Irish Republican Army-linked party, have tried since 1995 to block key Orange Order parades passing near or through Catholic areas. In 1998, seeking to defuse the annual flare-ups of violence, Britain empowered a civilian Parades Commission to impose restrictions on Protestant parades and Catholic counterdemonstrations.

Before Friday night's clash, the Parades Commission ordered the Orangemen's accompanying bands of fife and drum to play no tunes — some of which have anti-Catholic themes — as they passed the area and ordered the marchers' accompanying friends and family to use the far sidewalk in a separate group under police escort. The commission ordered the Catholics to protest peacefully.

The Protestants observed the restrictions, but Catholics on the far side of police lines threw a wide range of objects, including golf balls, at both the parade and their separated supporters as they got within range.

The senior Sinn Fein official at the scene, Gerry Kelly, blamed the police and Protestants for the violence. He accused Orangemen "of wanting to create tension" and said the violence was "a bad omen" for the rest of the summer.

But the member of British Parliament for north Belfast, Nigel Dodds, an Orangeman who participated in the parade, said it was a case of "thugs and gangsters attacking completely innocent civilians." He called for police to allow TV stations to broadcast footage of the riot.

The Orange Order, which has more than 50,000 members in this British territory of 1.7 million people, mounts its biggest yearly demonstrations on July 12 — an official holiday in Northern Ireland. On that date Orangemen commemorate the 1690 Battle of the Boyne, when an army led by the British Protestant king William of Orange defeated the forces of the deposed Catholic king, James II, in a river valley south of Belfast.