Police have clashed with protesters gathering in Tahrir Square in the Egyptian capital, Cairo, ahead of the second anniversary of the uprising that swept Hosni Mubarak from power.
President Mohammed Morsi’s opponents plan a rally, accusing the Islamist leader of betraying the revolution.
Mr Morsi denies the claim, and has called for “peaceful” celebrations.
An appeals court recently overturned Mr Mubarak’s life sentence over the deaths of protesters and ordered a retrial.
The 84-year-old former leader remains in detention at a military hospital.
On Thursday evening, police clashed with protesters who tried to remove barriers blocking a road to Tahrir Square.
The clashes continued overnight, as police fired tear gas at demonstrators camping on the square. At least eight people were wounded, officials said.
Mr Morsi’s Muslim Brotherhood party has not officially called for its own street rallies. It plans to mark the revolution by launching charitable and social initiatives