Preparations were under way on Tuesday for a mass rally in Cairo's Tahrir Square to protest against a decree by Islamist President Mohamed Morsi granting him broad powers.
Activists who have been camping out in the square since Friday were hoisting banners on lampposts slamming the Muslim Brotherhood, on whose ticket Morsi ran for office.
"The Muslim Brotherhood stole the revolution" read one banner. Another said the president was "pushing the people to civil disobedience."
A new clinic was set up in the middle of the square and dozens of ambulances were parked off Tahrir which has been closed off to traffic, an AFP reporter said.
Around the capital streets were quiet, with several schools closed for the day despite an education ministry statement saying that schools and universities would run as normal.
Marches are planned from across the capital into Tahrir, where the numbers are expected to swell after the end of the workday.
Demonstrations have also been called in several Egyptian provinces including Alexandria on the Mediterranean, in the Nile Delta and in central Egypt.
On Thursday, Morsi issued a decree that allows him to "issue any decision or law that is final and not subject to appeal", effectively placing him beyond judicial oversight.
The decree put him on a collision course with the judiciary and consolidated the long-divided opposition which accuses him of taking on dictatorial powers.