Egyptian opposition supporters are protesting across the country on the second anniversary of the uprising that swept Hosni Mubarak from power.
Police clashed with President Mohammed Morsi's opponents in Cairo, dispersing protesters outside his palace as thousands gathered in Tahrir Square.
Alexandria and Suez also saw clashes. In Ismailia, protesters set fire to the HQ of the Muslim Brotherhood's party.
Critics accuse Mr Morsi of betraying the revolution, which he denies.
The president has appealed for calm to end the clashes, in which at least 186 people have been injured nationwide.