Guinea's main opposition leader Celloun Dalein Diallo withdrew on Wednesday from a presidential election, alleging fraud, and will not recognize the outcome, his campaign director said.
His decision came as the national election commission began to announce early results from a vote held on Sunday that is expected to return incumbent Alpha Conde to a second five-year term in the West African country.
Figures from three of the capital Conakry's five communes showed Conde won 55 percent, 60 percent and 49 percent of the vote. All results must be ratified by the constitutional court.
Guinea has a history of political violence linked to ethnic tension, including protests during the 2010 campaign that brought Conde to power. On Wednesday police fired tear gas at protesters in the capital and the government called for calm.
"However the results turn out, we will see that they have nothing to do with reality. In any case, we will not recognize them," said Diallo campaign director Aboubacar Sylla.
Early radio announcements had Conde with a sizeable lead. Most analysts, though, expected results to be close enough to require a second round, most likely against Diallo. It was not clear how his withdrawal would affect the process.
Millions of voters, around 75 percent of the population, cast their votes in Guinea's second free election in nearly 60 years since independence.
Conde spent years in opposition to military leaders and was imprisoned and exiled. His election in 2010 ended two years of military rule. A year earlier, security forces killed over 150 people in a stadium in Conakry and raped dozens of women.
Sunday's voting was calm and won praise from international observers, though one monitor urged caution in declaring the whole election fair before results had been announced.
Tension has been mounting amid allegations by Conde's challengers of fraud. Last Friday, at least two people were killed and 33 injured in fighting between supporters of Conde and his main rival Diallo..
On Wednesday, anti-riot police in the suburb of Koloma Soloprimo fired tear gas and warning shots as protesters began building street barricades, residents said.
"It is heating up over here. We are all hiding in our houses," said resident Souleymane Bah.
A Reuters reporter on Monday saw three people with gunshot wounds at a local clinic after security forces and the opposition clashed overnight.
One of the injured, Bachir Barry, said he was hit in the hip as he was walking from the market.
"We are calling on everyone to give up on the street (protests). If the institutions are not respected, then there is no rule of law," Foreign Minister François Lonseny Fall said at a meeting attended by media and foreign diplomats on Wednesday.
Justice Minister Cheick Sako said at the same meeting that those caught protesting would face criminal charges.
Dozens of anti-riot police vehicles patrolled opposition neighborhoods, where burnt-out tyres and rocks littered the streets following the clashes late on Tuesday.