At least 25 people were killed Saturday in clashes which erupted in protest at an Egyptian court ruling sentencing 21 people to death for their role in deadly riots after a football match last year, DPA reported.
Seventy-three people, including sports officials and policemen, were charged with premeditated murder or negligence in connection with the rioting at Port Said stadium in February.
The riots broke out between rival fans of the hosts al-Masry and the visiting team al-Ahly following a Premier League match, killing 74 people. It was the country's worst football tragedy in more than a decade.
The verdict for the remaining 52 defendants will be given on March 9, the judge said. Most of the defendants did not attend the session, held in Cairo, for security reason.
All defendants have the right to appeal. None of those sentenced on Saturday were policemen.
In Port Said, clashes erupted between protesters and police forces. Al-Masry fans and families of the defendants say the case is politically-motivated.
At least two policemen were among the dead on Saturday, the ministry of interior said. Over 200 were injured.
Police used tear gas to disperse the crowd, who tried to storm the prison where defendants were being held.
However, hundreds of Al-Ahly team supporters, known as the Ultras, celebrated the verdicts by setting off fireworks and singing on the streets of Cairo.
The families of victims, who attended the reading of the verdict in court, shouted "God is great" as they carried pictures of some of those killed in the football riot.
Ahead of the verdict, Al-Ahly Ultras, who played a key role during the mass protests over the past two years, said that they will seek retribution if death sentences were not handed down.
After last year's match, al-Masry fans stormed the pitch and started attacking al-Ahly players and fans. Spectators were hit with knives and pushed from top of the stadium, according to witness accounts after the riots.
Al-Ahly Ultras accused police forces of conspiring against them with their rivals.
Saturday's clashes prompted army forces to deploy to Port Said, to protect vital institutions and restore security.
The decision came hours after troops were deployed in the nearby coastal city of Suez after clashes between police and anti-government protesters killed nine people.
The Suez clashes were the fiercest in a wave of violence that erupted across Egypt Friday, marking the second anniversary of a revolt that toppled former president Hosny Mubarak.
Egypt's biggest largest coalition threatened to boycott the upcoming parliamentary elections and called for mass protests next week, if their demands for political changes were not met.
"The National Salvation Front holds President Mohammed Morsi fully responsible for the excessive violence used by security forces against protesters and calls for an unbiased committee to investigate and punish those responsible for the bloodshed," it said.
They also called for suspending the Islamist-drafted constitution and forming a national rescue government.
The recent constitution referendum had left the country polarized, with the secular and liberal opposition saying the charter could undermine political and minority rights.
"In case these demands are not met in the coming days, the Front will call for mass protests on Friday to demand ... early presidential elections. The group also will not contest the next parliamentary elections without this comprehensive national solution," it added.
Morsi, Egypt's first civilian president, has cancelled a trip to Ethiopia where he was going to attend an African summit scheduled for Sunday.
He held an emergency meeting with the National Defence Council, which includes the ministers of defence, justice and information, to discuss the unrest in the country and how to hold accountable those responsible.
On Friday, Morsi appealed for calm and vowed that authorities would bring lawbreakers to justice.
"I call on all citizens to adhere to the noble principles of the Egyptian revolution in expressing opinion freely and peacefully," he said on his official Facebook page.