A large protest was held in Tahrir Square, Cairo, on Friday against the decision by Hosni Mubarak's former spy chief to stand in Egypt's presidential elections.
The protest was called by the Muslim Brotherhood, which wants the ruling military council to approve a new law banning former top Mubarak-era officials from standing.
They fear General Omar Suleiman and others seek to restore the old regime.
However, the BBC says the numbers in Tahrir Square were nothing like those that turned against the regime last January.
General Suleiman, 74, was the head of the General Intelligence Department for 18 years and briefly became vice-president during the protests that toppled Mr Mubarak last year.
He announced his candidacy for the presidency last Friday.
The Muslim Brotherhood has warned of turmoil if General Suleiman wins the election. It has put forward its own candidate of its own, Khairat al-Shater, despite earlier pledges not to contest the presidential elections.
On Thursday, parliament passed a law banning former senior officials who served under President Mubarak from standing for political office.
The presidential election is due to begin on 23 May. It is expected to go to a run-off in June between the top two candidates.