Egypt was thrust into a fresh crisis last night as security forces fired tear gas at protesters who returned to the streets of Cairo to demonstrate against the deaths of 74 football supporters on Wednesday.

In an emotionally charged day that followed Egypt's worse-ever sporting disaster, exacerbated by charges that security forces stood by and allowed rival fans to clash, nearly 10,000 gathered in Tahrir Square and outside the Interior Ministry, with some ripping down barbed wire around the building.

Resentment grew throughout the day as "ultra" supporters from Cairo's Al-Ahly -- one of Africa's most successful football clubs -- returned to the capital after Wednesday night's violence in Port Said that led to the club's fans being crushed to death trying to escape from the home Al-Masry supporters.

Hardcore groups of supporters of both Cairo's main clubs -- Al-Ahly and Zamalek -- were at the vanguard of those taking part in last year's revolution. "They want to punish us and execute us for our participation in the revolution against suppression," said the Al-Ahly ultras in a statement, vowing a "new war in defence of the revolution".

The protests had started as a peaceful march from Al-Ahly's headquarters to the area outside the ministry building near Tahrir Square.

Security forces guarding the area were separated from protesters by concrete blocks and barbed wire, but tensions rose as protesters advanced toward them, removing some of the barriers and hurling stones. Police responded with tear gas, sending demonstrators running. There were reports last night that gunshots had also been heard.

In scenes reminiscent of the clashes with police in November which left 40 people dead, protesters set tyres alight and motorcycles ferried some of those wounded to hospital as ambulances were unable to get through. Egyptian state TV said 100 people had passed out from the tear gas.

The Interior Ministry said in a statement that the protesters had cut the barbed wire and crossed over the concrete blocks to reach the roads leading to the headquarters. It urged the protesters "to listen to the sound of wisdom . . . at these critical moments".

In Port Said, it was becoming clear how so many people ended up dying when home supporters charged on to the pitch following their team's victory. One of the main exits in the stadium's eastern end -- a narrow, downward-sloping stepped corridor about 12ft wide -- was padlocked shut with a ceiling-high iron gate throughout the match.

As Al-Masry supporters charged towards the stand after the final whistle -- many wielding sticks and knives -- thousands of visiting Cairo fans fled into the corridor, the only way out for half of the people at the eastern end.

Doctors in Port Said yesterday said that most of those who perished in the crush died of asphyxiation. Hundreds more were rushed to hospital suffering from multiple fractures, caused as masses of people scrambled to escape the frenzy.

According to one health ministry official, all of the deaths were caused by stab wounds, brain haemorrhage and concussions, but Dr Mohammad Salah, who was working at Port Said's El-Amiri Hospital on Wednesday night, said none of the 31 bodies which arrived at his hospital had knife injuries.

The interior ministry said one policeman was killed, while a health official in Port Said claimed 1,000 people had been injured.