Opposition leader Felix Tshisekedi has been declared winner of DR Congo's presidential election, but his victory was dismissed by the runner-up and questioned by the Catholic church, clouding the vote's legitimacy and hopes of peace.

In a pre-dawn announcement, election officials named Mr Tshisekedi, son of the country's long-term opposition leader, provisional winner of the troubled vote to replace President Joseph Kabila. 

The news brought thousands of supporters onto the streets while others who had backed his opposition rival Martin Fayulu came out in protest. Four people died in unrest.

Mr Fayulu, who came a close second, denounced the result as an "electoral coup".

The Democratic Republic of Congo's influential Catholic church also said Mr Tshisekedi's victory did not tally with data collected by its own monitors. 

"These results have nothing to do with the truth at the ballot box," Mr Fayulu told Radio France International. 
"They have stolen the Congolese people's victory and the people will never accept that."

At stake is political stewardship of the notoriously unstable central African nation, which has never known a peaceful transition of power since independence from Belgium in 1960.

Election chief Corneille Nangaa declared Mr Tshisekedi the winner with 38.57% of the 30 December vote, just ahead of Mr Fayulu with 34.8%.

Mr Kabila's preferred successor, Emmanuel Ramazani Shadary, came a distant third with 23.8%.

Results of parliamentary elections, which were held alongside the presidential vote, are expected this evening and the pro-Kabila majority are already claiming to have won the house.

The last two elections in 2006 and 2011, both of which were won by Mr Kabila, were marred by bloodshed, and many fear a repeat of the violence if the result lacks credibility. 

Two civilians and two policemen were killed yesterday and another 10 people injured when a protest erupted in the western city of Kikwit, a Fayulu stronghold, police said.