A French judge has decided to investigate three African heads of state for money laundering and other alleged crimes linked to their wealth in France.

The probe follows a complaint by Transparency International France, an association that tracks corruption, against Gabon's Omar Bongo, Republic of Congo's Denis Sassou-Nguesso and Teodoro Obiang of Equatorial Guinea.

Association lawyer William Bourdon claimed Tuesday the decision was "unprecedented" for such a probe against heads of state.

A preliminary investigation turned up numerous signs of wealth among the three that Bourdon says belongs to their people.

The prosecutor's office opposed the opening of an investigation April 20 and now has five days to appeal the decision by investigating Magistrate Francoise Desset.

Bongo is among the last of the so-called "African Big Men" who came to power by the gun and resisted the democratic tide sweeping the continent. He faces little political opposition in his oil-rich West African nation, ruling through a mixture of patronage and quiet intimidation.

Last year, Bongo became the world's longest-ruling head of state, not counting the monarchs of Britain and Thailand. He has been in charge since 1967.

French media have reported his family owns abundant real estate in France — at one time with more Paris properties than any other foreign leader.

Equatorial Guinea is Africa's No. 3 oil producer. Its leader, Obiang, has faced several attempts to topple his government since he seized power in a coup three decades ago. His government is considered among Africa's worst human rights violators.

Sassou-Nguesso of the Republic of Congo seized power for a second time in 1997 with help from Angolan troops.