Guinean police have clashed with several hundred protesters in the capital, Conakry, as the country awaits the results of recent polls.
Tensions are rising in the West African nation after partial results suggested the outcome of the 7 November run-off was too close to call.
The electoral commission says it will publish results later on Monday, after missing earlier deadlines.
The polls aim to end 52 years of authoritarian rule.
Demonstrators on the streets of the capital burned tyres and threw stones at security forces in a part of Conakry inhabited by members of the Peul ethnic group.
"We managed to disperse the demonstration," a senior police official told Reuters.Alleged fraud
With more than half the votes counted, the race is tight, though former Prime Minister Cellou Dalein Diallo has a slight lead over rival opposition leader Alpha Conde.
Earlier on Monday, Mr Conde declared victory, claiming he had won three out of four regions.
Mr Diallo earlier threatened that he would not accept the outcome of the election, alleging fraud in two counties.
He claimed that his supporters in Kouroussa and Siguiri were too intimidated to vote after ethnic riots against the Peul in the days before the poll.
The election commission said it would investigate the allegations.
The candidates - Mr Diallo, 58, and Mr Conde, 72 - come from Guinea's two largest ethnic groups, the Peul and Malinke.
Meanwhile members of Mr Conde's Malinke community have claimed they have been attacked by Mr Diallo's supporters.
International observers noted the peaceful nature of the election and said there was a high turnout, but they have also warned the vote was just the start of the process.'Historic achievement'
Election commission head Siaka Toumany Sangare said the results would be published as soon as they came in, but the National Independent Election Commission website has not yet released any second round results.
Mr Diallo gained 44% of the first round vote in June, compared to 18% for Mr Conde. The opposition leader later complained of fraud.
Bernard Kouchner, foreign minister of former colonial power France, called the vote a "historic achievement after 50 years of dictatorship".
Guinea has been led since January by the interim government of Gen Sekouba Konate, who took over from the leaders of a 2008 coup.
The military seized power after the death of autocratic President Lansana Conte, who ruled the mineral-rich state for 24 years.
Despite being Guinea's largest ethnic group, a Peul has never been president. The Malinke are heavily represented in the ruling military junta.
Guinea is the world's largest exporter of the aluminium ore bauxite, yet the country is one of the poorest in West Africa.