Ali Ben Bongo wants to build on his father's legacy
Three different candidates say they gained the most votes in Sunday's election to choose a successor to Gabon's long-time leader Omar Bongo.
Mr Bongo's son, Ali Ben Bongo, veteran opposition leader Pierre Mamboundou and former minister Andre Mba Obame have all claimed victory.
The vote was generally peaceful but tense, with long queues of voters. No official results have been published.
Omar Bongo died in June after 41 years in power in the oil-rich country.
His son had been seen as the pre-election favourite, partly because he is the candidate of the ruling Gabonese Democratic Party (PDG).
PDG secretary-general Faustin Boukoubi said "the results are giving us victory".
Without giving further details, he said the results were "very close" in the capital Libreville but said the PDG had won in most rural areas and other towns, according to Radio France Internationale.
Mr Mamboundou said he was sure of victory and a "new era" had dawned in the country.
Mr Obame said he had won in four of the country's nine provinces, which represents 61% of total votes.
"Therefore I can tell you that according to my tally I am the candidate who received most of the votes and who will be announced the winner," he said.
The run-up to the election was marked by confusion with at least of the original 23 candidates pulling out in favour of Mr Obame, in a bid to unify the anti-Bongo vote.
However, other candidates denied reports that they had withdrawn.
One candidate, Cassimir Oye Mba, pulled out on polling day.
He said he did not want to vindicate a "calamitous electoral process which doesn't look like being clean and credible".
Several opposition figures have claimed that the PDG would use fraud to ensure Mr Bongo's victory.
Former colonial power France has praised the "good conduct" at the poll.
Interim President Rose Francine Rogombe has called for calm.
"Democracy is about accepting success and defeat," she said.
Ali Ben Bongo has promised to boost what he says is the prosperity that Gabon enjoyed during his father's years in power.
The vote was generally peaceful
But his rivals say there has been endemic corruption and favouritism in Gabon.
Omar Bongo was one of the world's richest men, with a string of properties in France.
He was an unflinching ally of France and a key element in French influence in Central Africa. But he denied corruption charges he faced in French courts.
BBC Africa analyst Martin Plaut says that Ali Ben Bongo is seen as less closely linked to the French elite than his father, despite being educated at the Sorbonne.
He is also somewhat detached from ordinary Gabonese, struggling to speak local languages with real fluency, our correspondent says.
Gabon is sub-Saharan Africa's fourth biggest oil producer and Africa's second biggest wood exporter, although most of its 1.4 million people live in poverty.