Bongo's victory in the August 27 vote was confirmed on Saturday by the country's top court
Ali Bongo will be sworn in on Tuesday as Gabon's president for a second seven-year term, his office announced, three days after his election victory was controversially validated by the constitutional court.
The ceremony will be held at the seafront presidential palace in Libreville, the presidency told AFP Monday. It gave no details of who had been invited or the time of the event.
"You don't get sworn in unceremoniously in secret," commented his main rival Jean Ping's spokesman Jean-Gaspard Ntoutoume Ayi, ironically.
Bongo's victory in the August 27 vote was confirmed on Saturday by the country's top court, which dismissed opposition claims of vote fraud.
But it received a cool reception internationally including from the African Union and the United Nations, while the European Union voiced regret that the election count had not been transparent enough.
Violence initially erupted on August 31 after Bongo, 57, was first declared the winner.
Demonstrators set parliament ablaze and clashed with police, who made a thousand arrests.
Opposition figures say more than 50 people were killed. The government has given a toll of three dead.
Ping, 73, who came in second in the vote, lashed the court's ruling as a miscarriage of justice and declared himself "president elect".
A career diplomat and a former top official at the African Union, he had filed a legal challenge after Bongo was declared the winner by a mere 6,000 votes.
Ping had asked for a recount in Haut-Ogooue province, where 95 percent of voters in the Bongo family stronghold were reported to have cast their ballots for the president on a turnout of more than 99 percent.
The Constitutional Court upheld Bongo's victory and put the winning margin higher at around 11,000 votes.
In its final tally, the court ruled Bongo had won 50.66 percent of the vote (172,990 votes) and Ping 47.24 percent (161,287 votes).
But the European Union's electoral observer mission said Sunday it "regretted" that Gabon's top court "had been unable to satisfactorily rectify anomalies observed during the count".
The African Union said it had "taken note" of the court's verdict, as did UN Secretary General Ban Ki-moon.
Former colonial ruler France deplored that the court verdict clearing Bongo's victory "has not lifted all the doubts" about the process.
Ping's campaign team said early Monday that he would meet foreign diplomats at his home later in the day, but the meeting did not occur.
Bongo's family has exercised a long grip on power in the oil-and mineral-rich country of 1.8 million people.
Ali Bongo took over from his father Omar Bongo, who ruled Gabon for 41 years until his death in 2009.
Cameroon's President Paul Biya, who is 83 and has held office since 1982, wrote to Bongo Monday voicing his "warm congratulations" and wishing him "success in the accomplshment of (his) new mandate."
Senegal's President Macky Sall also congratulated Bongo, as did Ivory Coast head of state Alassane Ouattara.
"In the delicate period which Gabon is going through, I want to express to you my full encouragement and hope passionately that dialogue and calm will predominate between all the parties," Ouattara wrote in a statement.