At least four people have died in clashes in Egypt as supporters of deposed President Mohammed Mursi demanded his reinstatement.
An Egyptian army vehicle fired live rounds in the direction of Muslim Brotherhood supporters.
They had been pushed back by security forces when they tried to enter Cairo's Tahrir Square.
Four people were killed in clashes in two neighbourhoods of Cairo.
All four were Brotherhood supporters, security sources said.
Egyptian authorities warned the Muslim Brotherhood against staging violent protests and tightened security in cities and strategic installations after the clashes.
Up to 1,000 Mursi supporters tried to reach the Rabaa al-Adawiya mosque area in northeast Cairo.
Security forces crushed one of their protest camps in August.
All but about 50 were turned back by police, who fired tear gas, security sources said.
Major General Sayed Shafiq, assistant interior minister for public security, denied any protesters had died in the southern city of Assiut.
Medical and health sources had earlier said four people had been killed in Assiut, without saying which side they were on.
In Cairo, onlookers threw rocks at pro-Mursi protesters, who hurled them back. Riot police earlier fired tear gas to push back the march.
By late afternoon, protesters had retreated from the area.
Members of the Brotherhood, which has been banned by court order, tried to reach the presidential palace but were turned back by police.
The state news agency said protesters failed in attempts to reach the defence ministry and a Republican Guard facility.
Fighting also erupted in Egypt's second city Alexandria and two Nile Delta cities.
The Brotherhood won every election after a popular uprising ousted autocrat Hosni Mubarak in 2011, but became deeply unpopular under Mr Mursi's rule.
Mr Mursi was accused of trying to give himself sweeping powers and entrenching the Brotherhood - allegations he denies.