ALGERIA’S defence ministry has announced that it has detained a suspected jihadist militant who was released this month by Mali as part of a prisoner swap, underscoring its fears of insecurity in the Sahel region. Mustapha Derar, an Algerian national, was arrested in Tlemcen after security forces tracked him from his crossing of the border into Algeria, the ministry said in a statement. Derar had joined a terrorist group in 2012, it added. Mali, grappling with an Islamist insurrection, released scores of prisoners including suspected militants early this month, days before jihadists freed four hostages: a Malian politician, a French…