At least 20 people were killed Sunday in a riot outside an Egyptian Premier League soccer match, the Associated Press reports. Security officials said the violence started when ticketless Zamalek fans tried to force their way into the game.

The riot broke out before a match between Zamalek and ENPPI at Cairo's Air Defense Stadium. Police used tear gas to disperse supporters, The Guardian reports. Security officials told the AP that some fans were killed in stampede and some were killed in clashes with police.

According to Zamalek supporter group Ultras White Knights' Facebook page, the death toll is as high as 22. The group shared a handwritten list of names of the alleged victims as well as gruesome photographs purported to be from the scene.

"The Zamalek fans tried to get in by force, and we had to prevent them from damaging public property," the Egyptian interior ministry ministry said in a statement provided to Ahram Online. According to The Guardian, the Air Defense Stadium is owned by the army.

UWK says that fans were tear-gassed as fans tried to enter the stadium through a single entrance: "a tiny metal fence surrounded by barbed wire being the only gate opened for us," Ahram reports.

In 2012, 79 people were killed in a brawl after a game in the Egyptian city of Port Said. Twenty-one people subsequently received the death sentence.

Ahram reports that Sunday's match between Zamalek and ENPPI proceeded despite the deaths outside the stadium. "Football is only for respectable fans," Zamalek board member Ahmed Mansour reportedly said on his Facebook page. "No thugs are allowed here."

Update, 4:30 p.m. – Here is video, uploaded to YouTube today, allegedly from the scene of the riot:

[Photo credit: AP Images]