At least 73 people have been killed in clashes between rival fans following a football match in the Egyptian city of Port Said, state television reports.
At least 1,000 were hurt as fans - reportedly armed with knives - invaded the pitch after a match between top-tier clubs al-Masry and al-Ahly.
Officials fear the death toll could rise further.
It is the biggest disaster in the country's football history, said the Egyptian deputy health minister.
"This is unfortunate and deeply saddening," Hesham Sheiha told state television. Continue reading the main story Analysis image of Jon Leyne Jon Leyne BBC News, Cairo
Football fans in Egypt can be violent, and certainly there is a bitter rivalry between these two teams.
The al-Ahly fans, known as Ultras, have a particular reputation for violence.
But lately they have been at the forefront of clashes with the police.
On the social media, there has been speculation - and I hasten to add there is no evidence - that the security forces may have had an interest in taking on al-Ahly supporters.
Certainly riot police did not seem to be very effective, they were standing around, but maybe there simply were not enough there.
At least 73 people have been killed in clashes between rival fans following a football match in the Egyptian city of Port Said, state television reports.At least 1,000 were hurt as fans - reportedly armed with knives - invaded the pitch after a match