State media in Mauritania says the country's government has handed Libya's former intelligence chief Abdullah al-Senussi over to Libyan authorities.
Libya wants to try Mr Senussi for crimes allegedly committed during his time as Colonel Muammar Gaddafi's right-hand man, the BBC reports.
Earlier in September, Mauritania's President Mohamed Ould Abdel Aziz said Mr Senussi must first face charges of illegal entry into the country.
Mr Senussi fled Libya after an uprising that toppled Colonel Muammar Gaddafi last year.
He is also wanted by France and the International Criminal Court.
According to reports, Mr Senussi was delivered to a Libyan official delegation headed by the minister of justice. His current whereabouts are unknown.