An Egyptian court has sentenced 21 people to death over football riots that killed 74 last year, with the verdict sparking fresh deadly violence. The riots - Egypt's worst-ever football disaster - began after a top-league game at Port Said stadium. The ruling caused anger in Port Said, where eight people died as supporters of the defendants clashed with police. The new violence comes after a day of unrest on the second anniversary of the uprising that ousted Hosni Mubarak. Thousands of people took to the streets on Friday to voice their opposition to Islamist President Mohammed Morsi, accusing him of betraying the revolution. At least seven people were killed and more than 450 wounded in unrest across Egypt. Last year's football riots led to the suspension of the league. They began minutes after the game in Port Said. Fans of local side al-Masry invaded the pitch, hurling stones and fireworks at visiting supporters from Cairo club al-Ahly. The violence in Port Said sparked riots in Cairo during which a further 16 people died. A section of al-Ahly supporters, known as the "ultras", played a prominent role in the protests against ex-President Mubarak. Some accused supporters of the toppled leader of instigating the Port Said violence. They also accused them of doing little to prevent it. All 21 defendants sentenced to death on Saturday were al-Masry fans. When the verdicts were announced by a judge in the Cairo court, relatives of victims cheered. However, the ruling sparked violence in Port Said, Supporters and relatives of those sentenced tried to storm the prison where the defendants are held. The eight people who died in the clash included two policemen, officials say. Army units were deployed on the city's streets following the violence. Seventy-three people, including nine policemen, were tried over the stadium clashes. None are al-Ahly fans. The judge said he would announce verdicts for the remaining defendants on 9 March. Economic 'collapse' Friday saw a big anti-government rally in Cairo's Tahrir Square, with opposition supporters clashing with police. There was also unrest in 12 out of 27 of Egypt's provinces. At least six of the deaths occurred in Suez. In Ismailia, protesters set fire to the headquarters of the Freedom and Justice Party, the political arm of the Muslim Brotherhood. The city's governorate headquarters was later also stormed. The liberal opposition accuses Mr Morsi of being autocratic and driving through a new constitution that does not protect adequately freedom of expression or religion. The government is also being blamed for a deepening economic crisis. One of the demonstrators at Cairo's Tahrir Square, Momen Asour, said he had come to demand an end to President Morsi's rule. "We have not seen anything, Neither freedom, nor social justice, or any solution to unemployment, or any investment," he said. "On the contrary, the economy has collapsed." President Morsi and his allies have dismissed the claim, saying they have a democratic mandate following recent elections. The constitution, drawn up by an Islamist-dominated body, was approved by referendum last month.