Senussi faces an international arrest warrant after a Paris court sentenced him in absentia to life for his alleged involvement in an attack on a French airliner in 1989 that killed 170 people, a statement from the Elysee said.
Senussi, a brother-in-law of Kadhafi is also wanted by the Hague-based International Criminal Court, ICC, for what is claimed was his crucial role in crushing the country’s popular revolt.
The ICC, which issued an arrest warrant for him in June last year, says he was an “indirect perpetrator of crimes against humanity of murder and persecution based on political grounds”.
And he could be held accountable for the Abu Salim prison massacre of 1996 when more than 1,000 detainees were gunned down.
Senussi was arrested overnight at Nouakchott airport after arriving on a regular flight from Casablanca, Morocco carrying a fake Malian passport, a Mauritanian security official said.
He was taken to the national intelligence agency's office in Nouakchott but it was unclear what the Mauritanian government planned to do with him, said the official.
Long considered Kadhafi’s right-hand man, Senussi remained faithful to the end to the man who ruled Libya with an iron fist for 42 years.