Thousands of Egyptians have protested in Cairo's Tahrir Square against a run for the presidency by former intelligence chief Omar Suleiman.
The Muslim Brotherhood, the biggest group in parliament, called the protest after Suleiman announced his candidacy last week.
His presidential bid has alarmed reformists, who regard him as a threat to their hopes for democratic change.
"Suleiman, do you think this is the old days?" chanted the protesters gathered in the square, the cradle of the uprising where Egyptians last year united to sweep Hosni Mubarak from power.
The square was mostly filled with Islamists, others boycotted, reflecting deep divisions in the reform movement.
Muslim Brotherhood supporters waved the group's green flag and the red, white and black Egyptian national colours.
"The people demand the fall of the regime!" they chanted, a slogan heard during the anti-Mubarak revolt. They also sang the national anthem and chanted "Down, down with military rule".
Several thousand Islamists protested in the northern coastal city of Alexandria.
Omar Suleiman played a major role in managing a Middle East policy which became the focus of ever sharper public criticism during Mubarak's last years in power.
The council of army generals that has been running Egypt since Mubarak was deposed is due to hand power to an elected president on 1 July.
The vote, Egypt's first real presidential election, is due to get under way on 23 May and will likely go to a run-off in June between the top two candidates.
Frontrunners include the Muslim Brotherhood's Khairat al-Shater, ultra-orthodox Salafi sheikh Hazem Salah Abu Ismail, ex-Arab League Secretary General Amr Moussa, and Ahmed Shafiq, who served as prime minister in Mubarak's last days in power.
The Islamist-dominated parliament on Thursday passed legislation that would stop both Suleiman and Shafiq from running on the grounds they served in top posts under Mubarak.
However, analysts doubt the law will be enacted by the ruling generals, setting the stage for more tension.
