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

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

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 North Circular Road took cover behind their armored vehicles after hearing bursts of automatic gunfire, although nobody was reported hit by bullets.

Later, riot police equipped with body armor, shields and flame-retardant boiler suits repelled the attackers with plastic bullets and mobile water cannons.

The rioting continued for several hours, spreading after nightfall to Ballyclare and Newtownabbey, two predominantly Protestant suburbs of Belfast. On Shankill Road, more than 1,000 people confronted police units, who responded with water jets and volleys of plastic bullets.

Protestant mobs also blocked several key roads to protest the authorities' decision to bar Orangemen from marching on most of Springfield Road, a predominantly Catholic area with one isolated Protestant section. Police forced the Orangemen to march instead through a derelict industrial site to their 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 several points, police and politicians reported that Catholic mobs had joined the maelstrom, with police facing attack from two directions.

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 mainly Protestant state 85 years ago.

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

Protestants set alight barricades in Belfast during clashes that injured more than a dozen people.