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 - the country's worst soccer disaster.
A demonstrator and an army officer were reported dead in Cairo and in the city of Suez two people were killed on Friday 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.
We will stay until we get our rights. Did you see what happened in Port Said? said 22-year-old Abu Hanafy, who arrived from work on Thursday evening and decided to join the protest.
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 Thursday.
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.
A Reuters witness heard firing and found gun pellets on the ground. Demonstrators had heaved aside a concrete barrier blocking a main road near the ministry overnight to get closer to the building.
We pulled it down with our bare hands, said Abdul-Ghani Mohamed, a 32-year-old construction worker. We are the sons of the pharaohs.
Ambulances had to intervene overnight to extract riot police whose truck took a wrong turn into a street full of protesters.
Police fired round after round of tear gas and the wind picked up on Friday afternoon to waft the fumes back to the police lines, leading the rioting protesters, some of whom waved soccer team flags, to cry God is Greatest.
Some of the demonstrators, mostly men in their late teens and 20s, goaded police defending the neat five-story ministry building, shouting The army, the police - one filthy hand.
DESTRUCTION IN SUEZ
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.
Rocks thrown by protesters littered streets that two months ago saw clashes between police and activists who view the Interior Ministry as an unreformed vestige of Mubarak's rule.
Hardcore football fans known as ultras, who often clash with the police and were at the forefront of the uprising against Mubarak, vowed to continue their protests.
The crimes committed against the revolutionary forces will not stop the revolution or scare the revolutionaries, said a pamphlet printed in the name of the ultras.
In Suez, witnesses said fighting broke out at a police station. We received two corpses of protesters shot dead by live ammunition, said a doctor at a morgue.
Police cordoned off the Suez state security headquarters and a Justice Ministry compound with razor wire and seven burned-out vehicles were nearby.
Many shops in Suez were wrecked and the facade of the Suez Canal Bank was destroyed. Police fired tear gas and shotgun pellets at protesters throwing stones.
The soccer stadium deaths have heaped fresh criticism on the military council that has governed Egypt since Mubarak stepped down. Critics regard the generals as part of his administration and an obstacle to change.
The army leadership, in turn, has presented itself as the guardian of the January 25 revolution and promised to hand power to an elected president by the end of June.
INTERIOR MINISTER BLAMES FANS
Health officials said at least 1,000 people were hurt in Port Said when fans invaded the pitch after local team al-Masry beat Cairo's Al Ahli, Africa's most successful club.
Hundreds of al-Masry supporters surged across the pitch to the visitors' end and panicked Al Ahli fans dashed for the exit. But the steel doors were bolted shut and dozens were crushed to death in the stampede, witnesses said.
The cause of the violence has been the focus of intense speculation. Some believe it was triggered by unknown provocateurs working for remnants of the Mubarak administration who are seeking to sabotage the transition to democracy.
Fans were puzzled at how match officials allowed the game to continue even as rival supporters threw stones and fired flares.
They also pointed to a thin police presence given the tense build-up to the game and a precedent of violence at such highly charged events.
Interior Minister Mohamed Ibrahim said the fans started it by insulting and provoking each other.
The public prosecutor ordered 52 suspects in the Port Said incident detained for 15 days pending investigation, state news agency MENA said.
They all face charges of premeditated murder, causing bodily harm, thuggery and destroying public property, MENA quoted deputy public prosecutor Abdul-Maguid Mahoumd as saying. The prosecutor will base his case partly on footage from 33 video cameras running in the stadium during the violence.
Ibrahim was widely blamed for the deaths during an emergency parliamentary session on Thursday. MPs including the Islamists who control some 70 percent of the chamber called for him to be held to account and accused him of negligence.
Safwat Zayat, an analyst, said the incident had done further damage to the image of the country's military rulers. The current events push in the direction of speeding up the transfer of power to civilians, Zayat said.
(Additional reporting by Ashraf Fahim, Ahmed Tolba and Omar Fahmy; Writing by Tom Pfeiffer; Editing by Louise Ireland)