At least 32 people have died after a furious crowd clashed with police in Egypt's Port Said, with another 41 killed in separate anti-government clashes in Cairo.
Among the dead are Abdel-Halim al-Dizawi, a who plays for the city's Al-Marikh football team, and Tamer al-Fahla, who used to play for al-Masri.
Both were shot dead.
The protesters were angered by the death sentences handed to 21 men for their involvement in last year's football stadium disaster in the city, which killed 74.
Spectators were crushed 1 February last year after Port Said's local team, al-Masri, beat Cairo's al-Ahly 3-1.
Yesterday's disturbances were sparked when Judge Sobhy Abdel Maguid announced that the men found guilty of involvement in the riot would be "referred to the Mufti," a phrase meaning execution, as in Egypt all death sentences require approval from the country's top religious authority.
Executions in Egypt are usually carried out by hanging.
Families of victims in the Cairo court cheered and wept for joy at the announcement.
A total of 73 people were standing trial, with more verdicts due on 9 March.
One relative of a victim in the court shouted: "God is greatest." Outside al-Ahly's stadium, supporters also cheered. Fans had threatened fresh violence unless the death penalty was given.
But in Port Said, al-Masri fans protested the decision outside the city's prison, where most of the convicted men are being held. Residents rampaged through the streets and some tried to storm the prison, angry that people from their city had been blamed, with gunshots reported.
At least 32 people are reported dead, two of them policemen, and state television quotes the Health Ministry saying more than 200 people were also injured.
Armoured vehicles and military police were deployed on the streets, with the state news agency quoting a general saying the aim was to "establish calm and stability in Port Said and to protect public institutions".
Unrest has been growing across Egypt since rallies began, marking the second anniversary of the protests which ended Hosni Mubarak's dictatorial 30-year reign.
Today police fired tear gas at dozens of stone-throwing protesters in Cairo in a fourth day of street violence that has killed at least 41 people.
Protesters are unhappy that the revolutionary fervour has since dissipated, alleging continued police brutality. President Mohamed Morsi, elected in June last year, stoked unrest with his decision to fast-track an Islamist-tinged constitution rejected by his opponents.
Morsi's supporters say their critics are ignoring democratic principles, after elections swept the Islamists to office.
Thousands have taken to the streets of Cairo, Alexandria and other cities since Friday.
Police fired tear gas to disperse protesters who had tried to cross barbed-wire barriers outside the presidential palace in Cairo, state TV reported. Protesters' tents were also dismantled and some burned.
In Cairo's Tahrir Square, Mahmoud Suleiman, 22, said: "We want to change the president and the government. We are tired of this regime. Nothing has changed."
"The protests will continue until we realise all the demands of the revolution - bread, freedom and social justice," said Ahmed Salama, 28, a protester camped out with dozens of others in Tahrir.
In a statement in response to Friday's violence, Morsi said the state would not hesitate in "pursuing the criminals and delivering them to justice". He urged Egyptians to respect the principles of the revolution by expressing views peacefully.
The president was due to meet yesterday with the National Defence Council to discuss the violence.
Foreign Office Minister Alistair Burt said such violence "can have no place in a truly democratic Egypt".
Adding that the UK remained a "committed as a strong friend of Egypt and the Egyptian people to support the aim of strengthening true democracy, he added: "The right to peaceful freedom of expression and assembly is an essential part of this, but the violence we have seen today can have no place in a truly democratic Egypt."