Muammar Gaddafi's former intelligence chief Abdullah al-Senussi faces charges in Mauritania for illegally entering the country, a source said.
Al-Senussi fled Libya after the fall of former Libyan leader Muammar Gaddafi and was arrested at the Nouakchott airport in Mauritania in March after flying in from Morocco.
The intelligence chief, who also was Gaddafi's brother in-law, is wanted by Libya, France and the International Criminal Court (ICC) but is now first set to face local charges in Mauritania.
Mauritanian officials said he would face trial for using false travel documents to enter the country.
A judicial source confirmed the move, telling AFP news agency: "Abdullah al-Senussi has been interviewed for the first time by the state prosecutor. He should face trial soon for illegal entry into Mauritanian territory."
The ICC wants his extradition for masterminding civilian attacks during the Libyan uprising in 2011, which led to the fall and death of Muammar Gaddafi. The court has said it would seek his extradition on two counts of crimes against humanity, murder and persecution.
Libya however had also demanded he be extradited to Tripoli to face trial for his alleged role in the killing of more than 1,200 inmates at Abu Salim prison, Tripoli, in 1996.
A third request for extradition was made by France where al-Senussi had already been convicted in absentia for a terrorist attack on a French airliner that exploded over Niger in 1989. The bombing killed 170 people, including 54 French nationals.
Mauritania's decision to try al-Senussi could now further delay his potential extradition to The Hague, Libya or France, though the Mauritanian authorities have yet to comment on its course of action in this regard.
The country also said in April that al-Senussi was suffering from health problems but did not provide any further details.