Throngs of young Egyptians incensed over a deadly melee at a soccer match clashed with security forces outside the Interior Ministry in Cairo on Thursday night as the episode threatened to plunge the country into a new vicious cycle of recriminations and violence.

More than 260 people were wounded Thursday night, mostly from tear gas inhalation, a Health Ministry official told state television. The Interior Ministry said in a statement that protesters were trying to tear down barricades to charge into the building.

Egyptian officials vowed to get to the bottom of Wednesday’s clashes in Port Said and declared a three-day period of mourning for the 74 people killed in a barbaric fight between rival fans after a game between regional teams.

Stunned by the evening’s savagery, which came in the wake of a string of rare violent incidents, Egyptians pointed to ominous plots by domestic and foreign agents they accuse of working to undermine the aims of the revolutionaries that dethroned President Hosni Mubarak a year ago.

The young, ardent soccer fans, known as “ultras,” who have become a fixture of protests targeting the country’s military rulers appeared convinced the fight had been somehow instigated by the generals.

“They killed our youth, they’re killing us,” said Aya Ibrahim, 21, a medical student who was among the thousands who streamed into Tahrir Square on Thursday afternoon. “They are totally responsible. This was planned. We will not allow any more blood to be shed.”

About an hour after the sun set, however, large crowds of young men, many waving flags of regional soccer teams, walked in huddles toward the Interior Ministry headquarters, a few blocks from Tahrir. Security forces sought to keep them from breaking into the building by firing rubber bullets and tear gas, witnesses said.

The scenes were reminiscent of deadly clashes in November between riot police and young protesters, many of whom were informally organized under the banner of the soccer teams they support.

Those fights were sparked after security forces used aggressive tactics to prevent demonstrators from setting up a permanent protest camp in Tahrir. The ensuing battles sparked a nationwide revolt against the country’s interim military leaders, who grudgingly agreed to a speedier transition to civilian rule than they had originally outlined.

Many Egyptians saw the day’s events as the most dramatic of what they believe is an orchestrated wave of politically-motivated mischief.

The Muslim Brotherhood’s Freedom and Justice Party, which won the most seats in the country’s newly elected parliament, issued a statement blaming “dubious forces that still have strong ties with the former regime.” In addition to that, the statement said, “there are, no doubt, foreign fingers that failed to take control of the Egyptian revolution.”

Mahmoud Ghozlan, a senior member and spokesman for the Brotherhood, said he believes foreign groups unhappy with the leading role of Islamists in post-revolutionary Egyptian politics are resorting to sabotage techniques.

“Foreign hands are paying money and training youth abroad to teach them to topple regimes, take down parliament and stage riots,” he said in an interview. “This was possible when we had a fraudulently elected parliament, but it isn’t possible or justified with the current freely elected one.”

Wednesday night’s clashes broke out at the stadium in Port Said at the conclusion of a match between the hometown Al-Masry and Cairo’s Al-Ahly, according to news reports and witnesses.

Witnesses said that shortly after the local team won, 3-1, fans of the other team streamed onto the field. Rival fans used sharp objects, rocks and metal pipes against each other, according to witness accounts and television footage.

Star Al-Ahly player Mohammad Abu Treika told the team’s television station that the national league tournament should be suspended indefinitely in light of the evening’s bloodshed.

“Crowds are dying in front of us, and there aren’t any police or security forces,” he said. “Football can go to hell if this is the situation.”

Television footage appeared to show security forces staying on the sidelines as the brawl intensified. The country’s police and army have, in recent months, been accused of using excessive force against civilians and failing to step in to stop unrest.

Sherif Ikrami, a goalkeeper for Al-Ahly, told a private television station that he felt powerless as hundreds of fans pounced on him and his teammates.

“I’m one of the players who has marks of the fight on his face,” he said, looking distraught. “It was a massacre. We’re not playing soccer again! What soccer are we going to play after 70 people died? What soccer?”

Al-Masry’s chief executive resigned shortly after the fight, saying carnage of that magnitude couldn’t have erupted spontaneously. “There are so many hands playing with our country so we can remain in the state of chaos and instability we are living now,” he said in a televised interview shortly after stepping down.