Libreville - President Ali Bongo Ondimba, whose father ruled oil-rich Gabon for 41 years, said Saturday that he will contest a presidential election in August.Bongo was elected for a first term in a disputed 2009 vote following the death of his father Omar Bongo Ondimba, who had steered Gabon from 1967 and was described by critics as a corrupt despot."There, I am officially a candidate," he said, after filing his papers for the August 27 poll.Jean Ping, a former African Union commission chief and a stalwart in the president's father's regime has already filed his nomination in a dramatic challenge to Bongo.Ping, born to a Chinese father and a Gabonese mother, had accused Ali Bongo of trying to force him out of the race through "Machiavellian" judicial means. A government spokesperson had threatened Ping with legal action over statements in which the former AU chief was said to have likened the regime to "cockroaches", accusing him of seeking to provoke civil war. Ping has said a video circulating on social media showing him making these comments was a montage.Some of the president's critics have opposed his re-election on the grounds that he was a Nigerian who was adopted in the 1960s and was therefore ineligible as a foreigner."Ali Bongo is incapable of proving his nationality. I have never considered him president of Gabon. Have you seen anyone with four birth certificates," Jean-Steve Okimbi, one of his opponents told AFP.Bongo's father Omar was president from 1967 until his death in 2009. This rule saw the country tap its new found oil wealth that led to a per capita income four times that of most sub-Saharan African nations.However, most of it has not trickled down to ordinary people. Critics accuse the Bongo family of usurping the country's riches and stifling democracy.