Belfast, Northern Ireland ? Crowds of Protestant hard-liners blocked key roads in Belfast and rioted for a third straight night Monday in a long-building explosion of frustration at Northern Ireland’s peace process.

At least 50 officers were wounded over the weekend when extremists fought riot police and British troops in the worst Protestant violence in a decade. The British governor and the territory’s police chief said two outlawed Protestant paramilitary groups mounted attacks on police.

The rampage followed British authorities’ refusal Saturday to permit the Orange Order, Northern Ireland’s major Protestant brotherhood, to parade as it usually does each year along the boundary of Catholic west Belfast.

Monday’s road blockades, formed by men, women and children, caused traffic jams that lasted for hours.

Protestant riots resumed at nightfall Monday in several parts of Belfast, although the mobs were smaller, the level of destruction much less severe and the intensity of violence greatly reduced from the weekend. No new injuries were reported.

Protestants threw fire bombs at a heavily fortified police base on the line between British Protestant and Irish Catholic turf in west Belfast. Gangs pelted passing cars on the city’s two major highways with stones, forcing police to divert traffic to smaller roads.

Several thousand police equipped with shields, body armor, flame-retardant suits, guns loaded with plastic bullets, armored personnel carriers, mobile water cannon and tear gas were on standby in fortified barracks across this city of 600,000. About 1,200 British soldiers also were deployed to support the police.

Confrontations over Protestant parades, particularly near Catholic areas, have triggered riots in the past. The most widespread violence happened from 1996 to 1998, when Catholic militants blockaded Protestants’ parade routes.

Since then, a government-appointed Parades Commission imposed restrictions on disputed Protestant parades. Until now, Orangemen usually accepted with sullen resignation.

But when the commission ordered Saturday’s marchers to parade through a factory site instead of the main road, Orange leaders called for illegal sit-down protests all over Belfast. Orangemen refused to accept any responsibility for the rioting.