Egyptian protesters are gathering in Cairo's Tahrir Square to mark the second anniversary of the uprising that brought down longtime leader Hosni Mubarak.
The secular-leaning political opposition is calling for protests Friday against President Mohamed Morsi and the Islamist Muslim Brotherhood party. Opposition leader Mohamed ElBaradei has used his Twitter account to call on protesters to "finally achieve the objectives of the revolution."
On Thursday, President Morsi urged people to stay calm and mark the anniversary peacefully. The Muslim Brotherhood has announced it will not take part in celebrations or protests, but will instead launch a charity drive.
But police skirmished overnight with some protesters near Tahrir Square who launched incendiary devices at them. Police answered with tear gas, and set some of the protesters' tents in the square on fire.
Rallies are also expected in Alexandria and other major Egyptian cities.