Egypt crisis: Dozens dead in Egypt 'day of anger'
More than 80 people have been killed in Egypt, officials say, as protesters loyal to the ousted President Mohammed Morsi clashed with security forces.
Most of the reported deaths were in Cairo, but about 25 were elsewhere, including 12 in Nile Delta cities.
Mr Morsi's Muslim Brotherhood said on Friday that there would be a week of daily rallies across Egypt.
Two days ago the protesters' camps were cleared, leaving at least 638 dead and sparking international condemnation.
In the wake of Wednesday's violence, the interior ministry says police have been authorised to use live ammunition "within a legal framework".
A state of emergency is also in force, including a dusk-to-dawn curfew.
'March of Anger'
Hundreds of people had gathered at a mosque in Cairo's Ramses square on Friday, after the Muslim Brotherhood, of which Mr Morsi is a member, appealed to its supporters to join a "march of anger".
The demonstrations took place under the slogan "the people want to topple the coup" - referring to the military's removal of Mr Morsi in early July.
The protests quickly became violent - the BBC's Jeremy Bowen says the trigger was when a police station came under fire.
He saw at least 12 bodies brought into a mosque near Ramses Square.
Gunfire was also heard on the banks of the Nile.
The Muslim Brotherhood said that Friday's protests would end at sunset prayers, approximately 20:00 local time (18:00 GMT).
However, disturbances were reported into the evening in the capital.
Security was tight in Cairo, with many armoured personnel carriers on the streets.
The army blocked off entrances to Tahrir Square, the focus of demonstrations that led to the toppling of President Hosni Mubarak in 2011.
Elsewhere in the country, at least five people were killed in the second city of Alexandria, six in Suez, eight in Damietta and five in Fayoum, according to medical sources.
Members of groups opposed to Mr Morsi - the National Salvation Front and Tamarod - called for counter-demonstrations in response to the Muslim Brotherhood protests.
There were also calls for people to protect their neighbourhoods and churches throughout the country, because some Islamists have accused the Coptic Church of backing Mr Morsi's overthrow.
Bishop Angaelos, General Bishop of the Coptic Church in the UK, told the BBC that about 50 churches had been attacked throughout the country since the break up of the protest camps.
"This time is normally the fast of St Mary, when there are normally vigils in the churches, but we are now limiting those because there is a danger to the congregations, " he told the BBC.
Wednesday's bloodshed has drawn widespread international condemnation.
- French President Francois Hollande has spoken to German Chancellor Angela Merkel and UK Prime Minister David Cameron, who says the "violence and repression is unacceptable"
- EU diplomats will meet in Brussels on Monday - some have called for EU aid to Egypt to be frozen
- EU foreign policy envoy Catherine Ashton said responsibility for the crisis "weighs heavily on the interim government, as well as on the wider political leadership in the country"
- UN under-secretary general Jeffrey Feltman will visit Cairo next week to discuss the situation with Egypt's authorities
- Turkey has described Wednesday's events as a "massacre" and recalled its ambassador to Cairo - in retaliation, Cairo has cancelled naval exercises with Turkey
But some other nations support the interim government's actions.
Saudi Arabia's King Abdullah issued a statement saying: "The Kingdom of Saudi Arabia, its people and government stood and stands by today with its brothers in Egypt against terrorism."
Mr Morsi, Egypt's first democratically elected president, was ousted by the military on 3 July.
He is now in custody, accused of murder over a 2011 jailbreak. His period of detention was extended by 30 days on Thursday, state media said.