President Vladimir Putin on Monday acknowledged for the first time that "radical Islamists" were behind last week's attack on a concert hall outside Moscow, but suggested they were linked to Ukraine somehow. Eleven people have been detained in connection with the attack, which saw camouflaged gunmen storm into Crocus City Hall, open fire on concert-goers and set the building ablaze, killing at least 139 people. "We know that the crime was committed by the hands of radical Islamists, whose ideology the Islamic world itself has been fighting for centuries," Putin said in a televised meeting.