Wednesday's football disaster in Port Said that left 74 people dead – mostly supporters of Cairo club Ahly – has provoked a fresh wave of violent protest and indignation across Egypt.

Amid widespread speculation and allegations, the People's Assembly on Thursday asked the commission charged with investigating protester deaths during Egypt's 2011 uprising to investigate the circumstances behind the country's first tragedy of 2012.

One of the first legal moves taken after the disaster was the detention of Port Said's security chief and head of police investigations, pursuant to a prosecutor general decision. This move failed to sooth rising public anger.

The ruling Supreme Council of the Armed Forces (SCAF) has borne the brunt of protesters' rage, with demonstrators in Cairo, Port Said, Suez, Alexandria and other governorates, insisting the SCAF had a hand in instigating the disaster.

Some distraught and weeping protesters chanted "down, down with the military council," and others demanded the execution of Egypt's de facto ruler Field Marshall Mohamed Hussein Tantawi.

On Thursday afternoon, thousands of protesters also converged on the interior ministry in downtown Cairo to denounce the suspected involvement of security forces in the disaster.

The peaceful protest turned violent as night descended, with stones thrown and tear gas launched, in scenes reminiscent of November's Mohamed Mahmoud Street clashes and December's violence after the forcible dispersal of a sit-in outside the Cabinet building.

Hours before the protests turned violent, many MPs at an emergency session of the People's Assembly blamed the disaster on PM Kamal El-Ganzouri's interim (SCAF-appointed) government and called for the sacking of Interior Minister Mohamed Ibrahim, both of whom were present at the session.

Some MPs echoed the sentiments of protesters by demanding the end of military rule, either by holding presidential elections earlier than the schedule date of June 2012, or by the appointment of a national salvation government to assume power until a civilian president is elected.

"There is a political crisis because the SCAF has lost its legitimacy, which it originally gained on 11 February by the power of the people," said liberal MP Amr Hamzawy during the session. "The main reason why the SCAF assumed power was to put an end to the bloodshed [during the revolution] and that still hasn't happened."

A full cabinet reshuffle and the dismissal of the prosecutor general was also suggested. However, the session did very little to ease growing tension and anger on the streets.

The Port Said disaster, which left 74 dead and hundreds injured during a league match between Masry and Ahly, occurred after the final whistle when the home fans stormed the pitch, chased Ahly players and staff down the tunnel and began attacking its supporters – mostly members of Ultras Ahlawy, the club's group of hardcore supporters.

According to varied accounts, many died in the ensuing stampede, while others were deliberately thrown off the stands or were stabbed to death.

Facts and theories

Many believe Tantawi and the SCAF instigated the disaster in revenge for Ultras Ahlawy members chanting for an end to military rule during their team's match against Arab Contractors on 28 January.

Whether the notion is a mere conspiracy theory or not, the fact remains that Wednesday's match was deemed exceptionally flammable days before it took place.

A perennial rivalry has existed between the two teams, and their matches have often been ill-tempered affairs and followed by fan scuffles. However, this year the violence reached unprecedented levels.

Ahead of the same fixture last season on 29 April 2011, hundreds of Ultras Ahlawy members had altercations with Central Security Forces (CSF) shortly after arriving in Port Said, and local residents claimed the group created havoc in the city, damaging public properties and even breaking into houses.

The Ultras Ahlawy stressed those days on their official website that they did not intend to destroy the city as widely believed:

"We arrived at 2pm amid what can be described as lacklustre security. We were told we had to be transported by the police [blue] vans, which are designated for prisoners, and of course we refused.

"Later on, they brought us two buses that only held 40 persons. When some of us got on, the Port Said fans destroyed the vehicles, so we had to get out of the station. By the time we were out, the Port Said crowd left ... We found ourselves alone in the face of the interior [ministry] forces that used intensive waves of tear gas against us."

Ahead of the Masry v Ahly match on 1 February, videos circulated on the internet showing Ultras Ahlawy youth fighting the police in the streets of Port Said, and accounts of residents accusing them of sabotaging the city in April 2011.

Some believe the videos were spread in an attempt to aggravate tensions before the match, others think Ahly supporters were bragging about what they had done, and therefore their Masry counterparts were eager to settle the score.

It is well known that there is no love lost between Ultras Ahlawy and the Central Security Forces (CSF), particularly since deadly clashes between the two during the revolution and beyond. It is the CSF that is responsible for security at football matches.

Feverish speculation on social networking sites has suggested the SCAF wanted to teach Ultras Ahlawy a lesson for both insulting Tantawi during the Arab Contractors' match in January and for its political activity since the revolution, which has usually been at odds with military rule.

Thus, so the speculation goes, the SCAF conspired with the police to allow Port Said hotheads to take their revenge against Ahly supporters for last year's events when Ahly fans trashed parts of their city.

Sherif Hassan, a journalist and expert on Ultras groups, told Al-Nahar TV: "I have attended many matches in my life and I know what football violence is like. What happened in Port Said [a few days ago] was way beyond that; there is no way football fans could be that brutal."

It is worth noting that other pitch invasions in Egypt last year witnessed no deaths or major injuries. No fatalities occurred on 2 April 2011, for example, when a much larger group of Zamalek fans stormed the Cairo Stadium pitch during their team's match with Tunisian side Club Africain in the African Champions League.

Bothaina Kamel, the only female Egyptian presidential candidate, commented that "What happened in Port Said is a premeditated murder and revenge against Ultras because they protected the revolution … The military council is leading the counter revolution."

The April 6 Movement (Democratic Front) is also convinced that the SCAF was behind the disaster, but for a different reason. "Why do calamities take place every time the State of Emergency comes close to an end?" read the movement's statement. "First the attacks on the Two Saints Church, then the Israeli embassy and now what happened in Ahly's game with Masry.

"We are fed up with the justification that the police are still unable to pull themselves together and have limited resources; a lot of revolutionaries saw the strength of the police during the Mohamed Mahmoud Street clashes and the cabinet violence," the statement added.

Aside from the speculation, it is a fact that at some point during Wednesday's match, the CSF deployed between the stands containing Ahly fans and those of home supporters mysteriously departed, leaving the away spectators completely exposed to attack. What is more, fans had no trouble getting onto the pitch after every goal. Masry came from behind to win the match 3-1.

"The police deliberately absented themselves from this match to increase the violence," said Mahmoud Hani, 21, who lost friends in the disaster. "It is clear that the fight was arranged and the security forces participated in this."

Ahly's veteran midfielder Mohamed Barakat, who announced his retirement from professional football after the disaster, told the club's channel during the chaos that "People have died, we are seeing corpses now. There are no security forces or army personnel to protect us."

Star playmaker Mohamed Abou-Treika, who also retired on Thursday, screamed while describing what happened, saying, "The security forces left us, they did not protect us. One fan has just died in the dressing room in front of me."

Pictures showing blood-stained seats in the Port Said Stadium, and victims with deep and vicious wounds, substantiated allegations that some assailants carried bladed weapons. The fact they had smuggled them inside the stadium further incriminates the police.

As the People's Assembly's fact-finding committee is yet to identify the truth of what happened in Port Said on 1 February, and its perpetrators are yet to be brought to justice, clashes between the police and protesters are widely expected to continue.