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, a witness said.
The state news agency MENA said 17 people had been injured in fighting after a funeral ceremony at the city's Coptic Orthodox cathedral. Public television showed riot police firing tear gas to disperse the crowd.
In some of the worst sectarian violence for months on Friday, four Christians and one Muslim were killed in El Khusus, north of Cairo, when members of both communities started shooting at each other.
New clashes erupted on Sunday when hundreds of angry Copts who had attended a funeral service at St. Mark's Cathedral spilled out into the streets of Cairo, chanting "With our blood and soul we will sacrifice ourselves for the cross".
After an emotional church service, where relatives of the dead wept, young Christians started hurling rocks at police officers, a witness said.
The protesters smashed six private cars and set two on fire, prompting an angry reaction from Muslims living in the neighbourhood, who threw stones at them, a witness said.
Christians have complained of attacks on churches by radical Islamists, incidents that have sharpened long-standing Christian grievances about being sidelined in the workplace and in law.
The president's office and top Muslim leaders were quick to condemn Friday's clashes, which happened after Christian children scrawled on the wall of a Muslim religious institute, according to witnesses.
Still, many Christians at the funeral called for Mursi and his Islamist allies to go, some of them chanting "The blood of Christians is not cheap, Mursi, you villain".