Gabon's President Ali Bongo has pledged to give his share of his father's inheritance to charity and said his family was also handing over properties including a villa in the capital and two hotels in Paris to the state.

Bongo has led the central African oil producer since winning a 2009 election that followed the death of his father, longtime President Omar Bongo.

Ali Bongo made the announcement in a speech broadcast on state-owned television late on Monday to mark the 55th anniversary of independence from France. He said the decision was in honour of his father.

"All the revenues from my share of the inheritance will go to a foundation for youth and education because everyone knows - and I say it again - that the youth were sacred in the eyes of President Omar Bongo Ondimba," he said.

Omar Bongo's heirs had together agreed to hand over to the Gabonese state a villa in Libreville that would house a university, he added.

Two hotels in the 7th and 8th arrondissements of central Paris would also be handed over to the state for "cultural and diplomatic use", Bongo said.

The Bongo family's wealth is believed to include millions of dollars held in foreign bank accounts, real estate and stakes in Gabon's main industries.

Gabon maintained excellent relations with France during Omar Bongo's four decade rule under a system known as "Francafrique", whereby France gave political and military support to leaders of its former African colonies in exchange for business favours.

The relationship has since cooled amid French investigations into ill-gotten gains that have focused on Gabon, Congo Republic and Equatorial Guinea.

France opened an investigation earlier this month into Bongo's chief of staff, Maixent Accrombessi, on suspicion he took a bribe from a French company that makes military uniforms.

Bongo's office criticised the investigation as an attempt to humiliate Accrombessi.

Gabon's oil wealth has put its per capita gross domestic product among the highest in Africa and the World Bank ranks it as an upper middle-income country. However, wealth is unevenly distributed and many Gabonese live in poverty.