At least 17 people have been killed in a protest in Cairo on Sunday against an attack on a Coptic church in southern Egypt.
Egyptian TV showed protesters clashing with security forces. Army vehicles were burning outside a State television building. Some 150 people were reported to be injured.
Christian Copts blame Muslims for the partial demolition of a Coptic church in Aswan province last week.
Sectarian tensions have increased since President Hosni Mubarak was deposed in a popular uprising on 11 February.
Coptic Christians - who make up about 10% of the population - accuse the governing military council of being too lenient on the perpetrators of a string of anti-Christian attacks.
Protesters on Sunday called on the council to sack the governor of Aswan province after the church was damaged on Friday.
The clashes began outside the State TV building in central Maspero Square and spread to Tahrir Square.
The BBC reports thousands joined in, hurling stones and tearing up the pavement for ammunition.