Protesters have blocked access to the Egyptian capital's largest government building and threatened to expand sit-ins to other sites unless authorities speed up reform efforts, including probing alleged abuses during the uprising that toppled President Hosni Mubarak.
The protest encampment underscored the growing frustration that political momentum has stalled since Mubarak's downfall in February.
The protesters want justice for the nearly 900 demonstrators killed by security forces during the uprising and seek a faster pace for trials of corrupt, Mubarak-era figures.
They blocked access to the central government administration building in Tahrir Square, the epicentre of the 18-day uprising. They also halted traffic and threatened to broaden the sit-ins to the nearby Interior Ministry and state TV building if their demands are not met.
On Friday, tens of thousands of people demonstrated in Cairo and several cities across Egypt to protest what they see as the slow pace of the current military rulers to cleanse institutions from Mubarak loyalists. Only several hundred protesters remained at Tahrir Square on Sunday.
In the city of Suez, east of the Egyptian capital, protesters have blocked the coastal road linking the Suez Canal city to the Red Sea ports of Safagah and Hurghada, disrupting maritime trade by trapping hundreds of cars and trucks.
Beside justice for the victims of the uprising, the protesters are demanding the resignations of Interior Minister Mansour al-Issawi, who is in charge of the hated police force, and the country's top prosecutor.
They also want to stop military trials for civilians and the release and retrial of civilians convicted by the military tribunals.
In an attempt to step up their campaign, protesters have called for massive, nationwide demonstrations on Tuesday to press their demands.
"We will not leave the square until all our demands are met," said Essam el-Shareef, one of the protest leaders.