Coptic Christians cover their faces from tear gas fired by police during clashes with Muslims standing outside the main cathedral in Cairo, April 7, 2013. Clashes broke out between Coptic Christians and Muslims in central Cairo on Sunday after the funeral of four Copts killed in sectarian violence outside the Egyptian capital on Friday night, witnesses said. REUTERS/Asmaa Waguih (EGYPT - Tags: RELIGION CIVIL UNREST)