China said Monday it had launched an international manhunt for the alleged mastermind behind an attack at a train station last month blamed on extremists from the Muslim Turkic Uighur ethnic group. FILE - In this Thursday, May 1, 2014 file photo, Uighur children play near a cage protecting heavily armed Chinese paramilitary policemen on duty in Urumqi in northwest China's Xinjiang Uygur Autonomous Region.