An Iraqi policeman stands guard outside the shrine of Imam Abbas as Shiite Muslims gather for the annual festival of Shaabaniya marking the birth of Imam Mahdi, revered by Shiites as the coming Messiah, in the central Iraqi city of Karbala on June 23, 2013. Mahdi is the 12th Imam who disappeared in the ninth centry and Shiites believe that he will appear before the end of time to establish justice and true Islam in the world.