The intelligence chief of former Libyan leader Muammar Gaddafi has been arrested in Mauritania, reports say.Officials said Abdullah al-Senussi was detained at Nouakchott airport.Mr Senussi, 63, was Col Gaddafi's brother-in-law, and has been described as one of his most trusted aides.He fled the country when Col Gaddafi was ousted and killed last year after an uprising and months of fighting. He is wanted by the International Criminal Court for crimes against humanity.Mauritanian security officials said Mr Senussi was arrested during the night as he arrived on a regular flight from the Moroccan city of Casablanca on a false Malian passport.Libyan officials have been unable to confirm the reports.Correspondents say Mr Senussi, nicknamed "the butcher", is one of the last significant members of the regime still at large.Libyan, Arab and western sources describe him as a thuggish figure who would personally beat and abuse prisoners.He was thought to have been responsible for purges of opponents within the regime in the 1980s and 90s, and for the deaths of 1,200 political prisoners at Tripoli's Abu Salim prison in 1996.