Masked and hooded Belfast Catholics hurled gasoline bombs, fireworks and other makeshift weapons at police into the night as the most bitterly divisive day on the Northern Ireland calendar reached an ugly end.

Several rioters and at least nine officers were injured, none seriously, when Irish nationalists in Ardoyne, a militant Catholic enclave of north Belfast, tried to block a parade Monday by the Orange Order, Northern Ireland's major Protestant brotherhood.

Tens of thousands of Orangemen spent Monday mounting hundreds of similar parades in an annual stress test for the province's fragile peace. Most passed peacefully, but a handful attracted violent protests that Catholic leaders blamed on Irish Republican Army dissidents opposed to Northern Ireland's joint Catholic-Protestant government.

At one point, masked Catholic rioters on store rooftops directed a deluge of Molotov cocktails, bricks and golf balls on riot police below