A pro-Morsi coalition has called for protests at the location of two sit-ins that were violently dispersed by security forces on 14 August, leaving over 600 dead.
Ali Khafagi of the Pro-Legitimacy and Anti-Coup Coalition called for supporters to gather on Sunday at Rabaa Al-Adawiya Square in Cairo and Nahda Square in Giza to commemorate the hundreds of victims.
The announcement was made on the website of the Freedom and Justice Party newspaper, a Muslim Brotherhood mouthpiece.
There would also be protests at other venues on Friday dubbed 'The Massacre of the Century', Khafagi said.
Rabaa and Nahda squares are sealed off by security forces on Fridays, the day usual day for protests. Morsi supporters have repeatedly tried to enter the two squares, sparking clashes with security forces.
Pro-Morsi protests have become smaller in recent weeks amid a severe crackdown on Islamists
Thousands of Morsi supporters have been arrested and hundreds killed in clashes with security forces and pro-military civilians since 28 June. More than a hundred policemen and dozens of anti-Brootherhood locals were also killed during the clashes.
Islamists have been accused of attacking security forces, police stations and the Christians. Such attacks have dramatically increased since Morsi's ouster.