Protestant extremists threw homemade grenades, gasoline bombs and other makeshift weapons Saturday and at least a dozen police and two civilians were wounded in the latest fury over a restricted Belfast (search) parade.

Protestants clashed with police, British troops and Catholic crowds in several parts of Belfast after authorities blocked the Orange Order (search) — the territory's major Protestant brotherhood — from parading past the hard-line Catholic end of disputed Springfield Road (search).

At least six officers were injured by flames and shrapnel from homemade grenades and gasoline-filled bottles on the nearby North Circular Road.

Officers on the North Circular Road took cover behind their armored vehicles after hearing bursts of automatic gunfire. In east Belfast, police said another six officers suffered mostly superficial injuries as they kept apart rival Catholic and Protestant mobs.

In rioting that ran from Saturday afternoon until early Sunday, police equipped with body armor, shields and flame-retardant boiler suits repelled the attackers with plastic bullets and mobile water cannons.

The mayhem spread at nightfall to Ballyclare and Newtownabbey, two predominantly Protestant suburbs of Belfast. Several buildings on Belfast's northern outskirts were set on fire.

Police said members of two outlawed organizations, the Ulster Defense Association and the Ulster Volunteer Force, were involved in the Protestant violence. Both groups are supposed to be observing cease-fires in support of Northern Ireland's 1998 peace accord.

But the commander of Northern Ireland's police force, Chief Constable Hugh Orde, said Orange Order leaders had inspired the violence. Trouble flared at several major roads and intersections where Orange leaders had instructed members and supporters to stage sit-down protests.

"The Orange Order must bear substantial responsibility for this. They publicly called people on to the streets. I think if you do that, you cannot then abdicate responsibility," Orde said.

On the Shankill Road, more than 1,000 people confronted police units, who responded with plastic-bullet volleys and water jets. A helicopter's spotlight overhead illuminated the mayhem. At least two civilians were injured.

Protestant mobs also blocked several key roads to protest the authorities' decision to bar Orangemen from marching on most of the Springfield Road, a predominantly Catholic area with one isolated Protestant section. Police instead forced the Orangemen to march through a derelict industrial site to their Orange lodge, which overlooks the road.

British army engineers erected truck-mounted canvas screens in hopes of blocking Catholics' view of the parade. But several hundred Catholics gathered on the road, and some stood on their rooftops to observe the drum-thumping procession. Both sides shouted vulgar abuse at each other.

Each summer, Northern Ireland endures inflamed communal tensions because of annual mass demonstrations by the Orange Order, a legal organization that was instrumental in founding Northern Ireland as a predominantly Protestant state 85 years ago.

Over the past decade, Catholic hard-liners led by Sinn Fein, the Irish Republican Army-linked party, have violently opposed Orange parades that traditionally passed near or through Catholic areas.

Northern Ireland's so-called "marching season" this year last turned violent on July 12, when several hundred Catholics attacked police with grenades, gasoline bombs and other weapons after an Orange parade passed the IRA power base of Ardoyne in north Belfast. About 100 officers and 10 civilians were wounded.