Gabon's opposition leader Jean Ping once more declared himself "president-elect" as he returned home Saturday, claiming he had the support of multiple foreign countries after a month abroad.

The re-election of President Ali Bongo in August sparked deadly unrest in oil-rich Gabon as Ping's opposition cried foul.

"All the embassies know with certainty that it was I, Jean Ping, who you elected president of the Gabonese Republic on August 27," Ping told supporters who turned out at the airport to meet him, while hundreds of others gathered at his headquarters in Libreville.

"The same embassies know that it was Ali Bongo who was the unlucky candidate in this presidential election," said Ping, who has spent the last month in Paris, Brussels and Washington and flew in from the French capital.

Ping filed a legal challenge after Bongo was declared the winner of the presidential election by a mere 6,000 votes, but in September Gabon's constitutional court confirmed Bongo's victory, dismissing opposition claims of fraud.

International powers have largely recognised the result while calling for political dialogue in Gabon.

At least three people were killed in post-electoral violence according to the government, while the opposition says at least 26 died and several others are missing.

Ping, a former top official at the African Union, said the final report of the EU's observer mission for the elections would "reveal the truth of the deception" when it is released in early December.

An initial report by the EU observers noted "evident anomalies" in the results, notably in Bongo's stronghold of Haut-Ogooue.

Ping's return to Libreville prompted a major security operation, with police controlling access to the airport and then blocking the fast lane of the route leading to the opposition's headquarters.

Bongo's family has exercised a long grip on power.

Ali Bongo took over from his father Omar Bongo, who ruled for 41 years until his death in 2009.