Nairobi/Libreville, Gabon  - Gabon's electoral commission was due Thursday to announce the winner of the presidential election amid growing tension and allegations of rigging.

Gabon went to the polls Sunday to elect a successor to Omar Bongo, who ran the oil-producing nation for more than 41 years until his death in June.

The electoral commission met Wednesday with the candidates and their representatives to discuss the results and resolve any complaints. The results were expected late Wednesday, but the meeting carried on into the small hours of Thursday morning.

Hundreds of opposition supporters gathered in a square near the electoral commission's building, surrounded by gendarmes armed with tear gas launchers, as the meeting went on, Radio France International (RFI) reported.

Three of the candidates claimed victory Monday, raising tensions in the capital, Libreville.

Representatives of Bongo's son Ali-Ben, former interior minister Andre Mba Obame and Pierre Mamboundou of the Gabonese People's Union all claimed they had gained enough votes for victory.

According to RFI, Mamboundou and Obame said Wednesday that the electoral commission was planning to hand victory to Ali-Ben Bongo with more than 50 per cent of the vote.

They were disputing these figures, saying their estimates gave him 30 per cent of the vote.

Ali-Ben Bongo, who has the support of the ruling Gabonese Democratic Party and by extension the army and police, is considered the favourite to win the race in the tiny West African country of 1.5 million people.

Omar Bongo ruled virtually unchallenged and gained the record of being the world's longest serving leader - no mean feat in a part of the world where coups have long been commonplace.

He was viewed as one of the ultimate political survivors, using corruption, cronyism and lashings of oil money to keep himself at the top for more than four decades.

Bongo died as French authorities were investigating whether he had used hundreds of millions of dollars of Gabonese public funds to buy dozens of lavish properties in France as most of the country's people live in poverty. (dpa)