Egyptian soccer fans rampaged through the heart of Cairo on Saturday, furious that seven police officers were acquitted while death sentences were confirmed against 21 people in the trial over the Feb. 1, 2012, stadium riot that left 74 people dead.

The stadium riot, in the city of Port Said at the northern tip of the Suez Canal, has taken on political undertones both because police faced allegations of negligence and because the verdicts were announced at a time when Egypt is in the grip of the latest and most serious bout of political turmoil in the two years since Hosni Mubarak was ousted.

The verdicts were handed down against the backdrop of an unprecedented wave of strikes by the nation's police force over demands for better working conditions and anger over what many believe are attempts by President Mohammed Morsi and his Muslim Brotherhood to take control of the police force.

Tensions over the riot — which began when supporters of Port Said's Al-Masry club set upon fans of Cairo's Al-Ahly club after the final whistle of a league game that the home team won — have fueled some of the deadliest street violence in months. Police guarding the stadium, meanwhile, faced allegations ranging from not having searched people entering the stadium to failing to intervene to stop the bloodshed.

Shortly after the verdicts were announced Saturday, angry fans of Cairo's Al-Ahly club, who had gathered in the thousands outside the team's headquarters in central Cairo, went on a rampage, torching a police club nearby and storming Egypt's soccer federation headquarters before setting it ablaze.

The twin fires sent plumes of thick black smoke billowing out over the Cairo skyline, prompting Defense Minister Abdel-Fattah el-Sissi to dispatch two army helicopters to extinguish the fires.

At least five people were injured in the protests, a Health Ministry official told the MENA state news agency.

Some demonstrators in Port Said also burned tires on the city's dock to prevent vessels from coming in and released speedboats into traffic lanes of the Suez Canal in attempts, foiled by the navy, to disrupt shipping in the vital waterway linking the Red Sea to the Mediterranean.

A spokesman for the Suez Canal Authority said shipping was not affected and 41 vessels transited the waterway on Saturday.

General unrest also continued elsewhere in the Egyptian capital, which has seen unrelenting demonstrations and clashes between security forces and an opposition that accuses Morsi of trying to monopolize power in the hands of his Islamist allies.

Two protesters also were killed and 19 injured in clashes elsewhere in the capital. These appeared to be unrelated to the soccer violence, national ambulance service chief Mohammed Sultan said. The fighting occurred near two luxury hotels and the U.S. and British embassies.

The court's decision upheld the death sentences issued in late January against 21 people, most of them Port Said fans. The original verdict touched off violent riots in Port Said that left some 40 people dead, most shot by police.

On Saturday, the court announced its verdict for the other 52 defendants in the case, sentencing 45 of them to prison, including two senior police officers who received 15-year terms each. The two were charged with gross negligence and failure to stop the killings.

Twenty-eight people were acquitted, including seven police officials.

Defense lawyers claimed the case was flawed from the start, with prosecutors collecting evidence in an "unorthodox" fashion and overlooking key aspects of the tragedy such as the fact the floodlights were turned off during the attack on the Al-Ahly fans and the nearest exit gate was locked. Many of the 74 victims died of suffocation or blows to the head.

Morsi's aides denounced Saturday's violence and sought to dismiss the notion of a country in chaos.

Ayman Ali, a senior presidential aide, called on the media not to provide a "political cover" to the violence sweeping the country and dismissed as exaggerated claims that the country's police force was in disarray.

Another presidential aide, Bakinam el-Sharqawy, lamented that the focus on protests and violence created an image of instability in Egypt that kept foreign investors away.

In anticipation of more violence, authorities beefed up security near the Interior Ministry, which is in charge of the police force, with riot police deploying in the streets around the complex in central Cairo.

The president of international soccer governing body FIFA appealed for calm.

"I call on football fans in Egypt to remain peaceful. Violence is never a solution and is contrary to the spirit of sport," Sepp Blatter tweeted.

Earlier, at the courthouse, Judge Sobhi Abdel-Maguid read out the verdict live on TV, sentencing five defendants to life in prison and nine others to 15 years in jail. Six defendants received 10-year jail terms, two more received five years each and one defendant received a 12-month sentence.

The court's decision on the nine Port Said security officers on trial was among the most highly anticipated — and potentially explosive — verdicts. In the end, the judges sentenced the city's former security chief, Maj. Gen. Essam Samak, and a colonel to 15 years in prison each, while the others were acquitted.

Al-Ahly's fans accuse the police of collusion in the killing of their fellow supporters, arguing that they had advance knowledge of plans by supporters of Port Said's Al-Masry to attack them. They also accuse them of standing by as the Al-Masry fans attacked the visiting Al-Ahly supporters.

The court rulings can be appealed before a higher court.

Many residents of Port Said say the trial is unjust and politicized, and soccer fans in the city have felt that authorities were biased in favor of Al-Ahly, Egypt's most powerful club.

In Port Said, a city that for weeks has been in open rebellion against Morsi, the Islamist leader, several hundred people, many of them relatives of the defendants, gathered outside the local security headquarters to vent their anger. They chanted slogans against Morsi's government and the verdicts. Police pulled out of the city on Friday after days of battling protesters in deadly clashes. The army has taken over security in the city, a move that was warmly welcomed by residents.

Some people in a cafe watching the verdict live on TV hit their heads in frustration, while others broke down and wept. Some said they could live with the verdict because an appeal leaves room for hope.

"There's still an appeal process. God willing, our rights will be restored," said Islam Ezzeddin, a local soccer fan. "We are not thugs. I hope to God when there's an appeal, that we feel we live in a country of law and justice."

However, the national railways chief, Hussein Zakaria, ordered trains headed to Port Said to terminate their services at Ismailiya, another Suez Canal city south of Port Said. He said the measure was taken out of fear for the safety of passengers.

Late on Saturday, activists in the city declared the start of a new general strike, with bands of protesters moving around the city pleading with business owners to shut down.