Protesters gathered in Cairo's Tahrir Square on Friday for what was billed as a mass rally to reclaim the revolution amid anger over the military rulers' handling of the transition.
Thousands flocked to the epicentre of protests that toppled president Hosni Mubarak in February to demand an end to military trials of civilians, cleansing institutions of former regime remnants, amendment of a recently published electoral law and social justice.
US film star Sean Penn was among the crowd, holding an Egyptian flag, accompanied by Egyptian actor and political activist Khaled al-Nabawi.
The powerful Muslim Brotherhood said on Wednesday it had decided to stay away from the demonstration.
Several marches were planned for Friday afternoon from around the city into Tahrir Square, including by political parties and several pro-democracy groups.
An AFP reporter estimated the number of protesters in the mid-afternoon at around 3,000.
Preacher Mazhar Shaheen, delivering the Friday Muslim prayer sermon, vowed to protect the goals of the revolution that toppled Mubarak.
He urged Egypt's military rulers to activate a law that prevents members of Mubarak's now dissolved National Democratic Party "who contributed to the corruption of political life" from running for public office.
Shaheen also called for amending a new electoral law, which stipulates that two-thirds of parliament be elected on a list system and one third as independents.
The aim would be "to prevent powerful individuals from controlling votes by hiring thugs to bully voters." Under Mubarak, influential businessmen associated with the regime were known to hire people to bribe or harass voters into picking them.
On Tuesday, the Supreme Council of the Armed Forces (SCAF), which took power when Mubarak was ousted, laid out the timetable for the first post-Mubarak elections, which will start on November 28 and take place over four months.
Presidential elections are expected to be set next year.
The Democratic Coalition, which groups dozens of parties including the powerful Muslim Brotherhood and the liberal Wafd party, have threatened to boycott the vote.
They object to Article Five of the electoral law, which bans political parties from running in a third of the seats in parliament, which are reserved for independents.
They fear the measure would help return old regime figures to parliament.
Under Mubarak, candidates affiliated with his party used patronage or pressure to garner votes.
Activists say that a proportional list system would help avoid that because voters would be electing candidates based on a party's political platform, circumventing candidates' personal power and influence.
On Thursday, six presidential hopefuls, including former Arab League chief Amr Mussa, issued a statement denouncing what they say is the military's extension of the transition period.
They called on SCAF to provide a clear road map, which would ensure that presidential elections are scheduled for no later than March 2012.
On the eve of Friday's protest, SCAF warned against any threat to democracy and national security and "those who seek to impede the democratic transformation that began with the call for parliamentary elections."
"Those who have called for the Friday (protest) bear the responsibility to organise and secure and protect all private and public property," SCAF said.
"Any encroachment on army units or camps or important establishments will be considered a threat to Egyptian national security and will be dealt with with the utmost firmness."
But in a statement published on Facebook, the pro-democracy April 6 movement objected to the military's depiction of activists as troublemakers.
Military ruler Field Marshal Hussein Tantawi has repeatedly stressed the army's commitment to democracy, but protesters have maintained pressure on the military council he presides over because of the slow pace of change.
Thousands of protesters have gathered in Tahrir Square on an almost weekly basis to rally for speedy reforms.
