Opposition leaders had urged voters to stay away, saying the government had inflated the electoral roll figures. Voting was slow, with no queues reported at polling stations in several parts of the country.

 Earlier in the day, Sassou-Nguesso told a rally of his supporters in the capital: "Fear not and go and vote. There will not be any more war in Congo."

 But his main rival, Mathias Dzon, and four other candidates had urged voters to boycott the polls.

 "No-one should go and vote on Sunday. Stay at home - we don't want an electoral hold-up or a parody of an election," said Clement Mierrassa, head of the opposition Congolese Social Democratic Party.

 Government officials say more than two million people have been registered to vote but Roger Bouka Owoko, head of the Congolese Observatory for Human Rights (OCDH), said that figure was "grotesque".

 "Congo cannot have so many electors," he said. "This monstrous electoral register is the drawback of the electoral process."

 The head of the European Commission delegation in Congo, Miguel Amado, said he also had concerns about the electoral roll being used and said many people had not received voting cards.