BELFAST (Reuters) - Northern Irish police came under gunfire and petrol bomb attack in the fifth night of violence in Londonderry late on Tuesday on the eve of a major annual parade in the British province that frequently triggers sectarian violence.

Three decades of fighting between mostly Protestant loyalists who want Northern Ireland to remain part of the United Kingdom and mainly Catholic Irish nationalists who want it to be part of a united Ireland, ended after a 1998 peace deal but the annual parades often revive tensions.

The Police Service of Northern Ireland (PSNI) said the gunshots were “a blatant bid to murder police officers”, escalating the simmering violence involving Catholic youths.

While no officers were injured in the shooting in the Bogside nationalist area of the city, two police officers and a civilian were hurt in street violence 24 hours earlier.

“I think this has now taken a nastier turn and it’s clear that people in dissident republicanism are trying to use the disorder for their own ends,” Colum Eastwood, leader of the moderate nationalist Social Democratic and Labour Party (SDLP), told Irish national broadcaster RTE.

Police in riot gear were also targeted in east Belfast and vehicles were hijacked and set alight when Protestant youths lit a massive bonfire. Large bonfires are traditionally lit in Protestant areas to mark the eve of the July 12 parades.

Thousands of Pro-British Protestants hold the marches in the British-ruled province every year to mark a 1690 victory by King William of Orange that sealed Protestant domination, a tradition Catholic Irish nationalists consider provocative.

The parades mainly ended without violence in recent years for the first time in decades.