Cairo clashes leave 24 dead after Coptic church protest
Clashes broke out after a protest in Cairo against an attack on a church in Aswan province last week which Coptic Christians blame on Muslim radicals.
Egyptian TV showed protesters clashing with security forces as army vehicles burned outside the state TV building.
A curfew is in force. The cabinet is to hold an emergency meeting on Monday.
Sectarian tensions have increased in recent months in Egypt.
The Copts - 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.
Prime Minister Essam Sharaf appealed to Egyptians not to give in to sectarian strife.
"What is taking place are not clashes between Muslims and Christians but attempts to provoke chaos and dissent," he said on his Facebook page.
State TV has announce a curfew in some parts of Cairo from 02:00 to 07:00 local time (00:00 to 05:00 GMT).
Thousands - mainly but not exclusively Christians - joined the initial march from the Shubra district of northern Cairo to the state TV building in Maspero Square where they intended to hold a sit-in.
They were calling on the military council to sack the governor of Aswan province. They also accused state TV of fanning the flames of anti-Christian agitation.
But the demonstrators said they were assaulted by attackers in plain clothes before the clashes with the security forces broke out.
The clashes began outside the state TV building but soon spread to Tahrir Square, the epicentre of the demonstrations which led to President Mubarak's resignation.
Thousands joined in the street violence, hurling stones and tearing up the pavement for ammunition.
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