Egyptian police fired tear gas outside Cairo's Coptic cathedral on Sunday after clashes following funeral prayers for four Christians killed in sectarian clashes. Black-clad riot police pointed at the main gate of the cathedral and fired the tear gas, television footage showed, as Coptic worshippers sought refuge inside the building. Witnesses said the mourners who were chanting against the ruling Muslim Brotherhood were pelted with stones as they came out of the cathedral. Reports suggest security forces also fired birdshot into the cathedral, injuring mourners and journalists. In a statement, the Interior Ministry said "a number of mourners began to damage cars in the area which led to confrontations with residents of the area." Television footage showed scenes of chaos outside the cathedral in the central Cairo neighbourhood of Abbassiya where Coptic bishops had been calling for peace and calm after the killing of the Christians on Friday. Loud bangs could be heard, as clouds of smoke rose up into the sky and people ran in several directions. At the service, the congregation chanted against the Muslim Brotherhood of President Mohammed Morsi. One Muslim was also killed in the clashes which flared on Friday night in Al-Khusus, a poor area in Qalyubia governorate, after a Muslim in his 50s objected to children drawing a swastika on a religious institute. The man insulted Christians and the cross, and an argument broke out with a young Christian man who was passing by, escalating into a gunbattle between Muslims and Christians in which assault rifles were used. Christians form between six and 10 percent of Egypt's population of nearly 83 million people.