Rock-throwing protesters fought riot police through clouds of tear gas near Egypt's Interior Ministry on a second day of clashes triggered by the deaths in Port Said of 74 people.
A demonstrator and an army officer were reported dead in Cairo and in the city of Suez two people were killed as police used live rounds to hold back crowds trying to break into a police station and fought in front of the state security headquarters, witnesses and the ambulance service said.
Hundreds of protesters blocked roads near state security headquarters in Egypt's second-largest city Alexandria.
Most of those killed in the Port Said football stadium on Wednesday night were crushed in a stampede and the government declared three days of mourning.
Protesters hold the military-led authorities responsible.
It was the country's deadliest incident since an uprising ousted Hosni Mubarak almost a year ago and it gave fresh impetus to regular street protests against Egypt's ruling generals.
The ministry in Cairo, a focus of hatred for football fans who say lax policing was to blame for the stadium disaster, has been hemmed in by street battles since yesterday.
Thousands staged running battles with riot police throughout Friday, ignoring government appeals to end the violence.
Tens of thousands were protesting peacefully nearby in Cairo's landmark Tahrir Square after 28 youth activist groups and political parties called for a "Friday of Anger".
Ambulances had to intervene overnight to extract riot police whose truck took a wrong turn into a street full of protesters.
Almost 1,700 people had been hurt by late morning in the latest confrontations in Cairo and 207 in Suez, the Health Ministry said, many of them from inhaling tear gas.
An army lieutenant was killed by a security vehicle that ran over him by mistake, Health Ministry officials said.