At least 74 people have died and around 250 are reported injured after violence flared at the end of a football match in Egypt.
The violence follows a year of unrest in the North African state, which saw President Hosni Mubarak removed from power in one of the early charges of the Arab Spring.
Wednesday's violence was sparked by a pitch invasion at a game in the northern coastal city of Port Said.
The fighting began after fans of Al Masry, the home team, flooded the pitch following a rare 3-1 victory over rivals Al-Ahly, the country’s top team.
Missiles, flares and bottles were thrown as fans chased players from rival teams, who fled to the dressing rooms. Some were reportedly injured. State TV showed fights breaking out across the pitch. The losing team’s manager was attacked.
Reuters reported that the Egyptian Army was sent to the stadium to ensure the security of the players, who were eventually removed from the ground. Field Marshal Hussein Tantawi, the head of the military regime, met the Al-Ahly team at an air force base near Cairo after they were flown back on a military aircraft.
"This will not bring Egypt down," said Tantawi. "These incidents happen anywhere in the world. We will not let those behind it go... This will not affect Egypt and its security."
Despite the presence of hundreds of police officers, security services seemed helpless to stop the melee as rival fans attacked each other with whatever weapons they could find.
The Egyptian Health Ministry told state TV that hundreds had been injured. According to the Associated Press, Egypt's state prosecutor has ordered an immediate investigation. Parliament is expected to convene an emergency session, while all further football matches have been suspended.
Hesham Sheiha, Egypt's deputy health minister, told state TV: "This is unfortunate and deeply saddening."
One of the Ahli players, Mohamed Abo Treika, spoke to local TV. He said: "This is not football. This is a war and people are dying in front of us. There is no movement and no security and no ambulances. I call for the premier league to be cancelled. This is horrible situation and today can never be forgotten.”
According to Sky News, some of the dead include security officials.
The riot is being described as the worst incident of football violence since 1996 when 78 people died at a World Cup qualifying match between Guatemala and Costa Rica.
Following news of the clashes in Port Said, a match between Al-Ismaili and Zamalek in Cairo was cancelled, which led to parts of the stadium being set alight by fans. The fires were quickly put out and no injuries were reported.
According to the BBC, supporters of al-Ahly, known as the Ultras, are "notoriously violent", and have been "heavily implicated" in confrontations with the police during the recent political unrest.