Thousands of police have clashed with protesters for control of downtown Cairo's Tahrir Square, leaving at least 81 people injured and four arrested.
The violence comes just nine days before Egypt's first elections since the ouster of Hosni Mubarak, the former president, in February.
Witnesses said clashes erupted after riot police dismantled a small tent camp set up to commemorate protesters killed in the earlier revolt and attacked around 200 peaceful demonstrators who had camped out in the square overnight.
Al Jazeera's Sherine Tadros reports from Cairo.
