At least 73 people were killed when fans rushed the field and rioted after a soccer game in Egypt on Wednesday, a health ministry spokesman said.

The clashes left at least 1,000 people injured, 150 of them critically, spokesman Dr. Hisham Shiha said. Most of the injured had concussions and deep cuts, he said.

The fighting occurred in a stadium in the northeastern city of Port Said after the home Al-Masry team beat Cairo's Al-Ahly team 3-1.

Fans from both sides bashed each other with rocks and chairs, said Mohamed Sultan, head of the ambulance association in Port Said.

Many of those who died fell from bleachers inside the stadium, according to Ahmed Saeed, an official from the Port Said governor's office.

Rescuers treated 60 people on the ground, Sultan said, and dozens of ambulances were at the stadium.

Authorities have been dispatched to hospitals to interview the wounded and investigate what caused the clashes, said Adel Saeed, a spokesman for Egypt's general prosecutor.

Egypt's military deployed two planes to transport the Al-Ahly team, some of its fans and some of the injured back to Cairo, he said.

Hundreds of angry fans gathered outside the club's headquarters in Egypt's capital, vowing revenge.

"This is a plot to stir violence in Egypt. Why would a winning team attack others ... and kill them? We will not let this one go," Al-Ahly fan Ahmed Tabaei said.

While authorities were responding to the fighting in Port Said, a fire broke out during a match in a Cairo stadium. It was not immediately clear whether the incidents were related.

Lawmakers were scheduled to discuss the situation in an emergency session of Egypt's parliament Thursday.

Sepp Blatter, president of the sport's international governing body, FIFA, said he was "very shocked and saddened" by the events.

"This is a black day for football. Such a catastrophic situation is unimaginable and should not happen," Blatter said in a statement.

The large death toll from the fighting is unprecedented in Egyptian soccer, CNN contributor James Montague said.

"It's not unheard-of to have organized violence between football clubs (in Egypt), but something on this scale has never been seen before," said Montague, who researched soccer in the Middle East for his book "When Friday Comes: Football in the War Zone."

During Egypt's revolution, well-organized groups of soccer fans became a powerful force for political change, he said. Soccer was also closely tied with former Egyptian President Hosni Mubarak's government, which used the sport to boost his popularity, Montague said.

But it was unclear whether political fury fueled Wednesday's clashes.

"There's been a security vacuum, so we don't know whether it's that or whether there's a Mubarak element to it. We just don't know at the moment," Montague said.