Egyptian protesters torched buildings in Cairo and tried unsuccessfully to disrupt shipping on the Suez Canal, as a court ruling on a soccer riot led to widespread unrest.
The ruling enraged residents of Port Said by confirming death sentences imposed on 21 local soccer fans for their role in the riot last year when more than 70 people were killed.
But the court also angered rival fans in Cairo by acquitting a further 28 defendants that they wanted punished.
Those acquitted included seven members of the police force.
Security sources said one person had died in Cairo from the effects of tear gas and 65 people were injured, some by rubber bullets.
The protests and violence underlined how Islamist President Mohammed Mursi is struggling - two years after Mubarak's overthrow - to maintain law and order at a time of economic and political crisis.
On Thursday Egypt's election committee scrapped a timetable under which voting for the lower house of parliament should have begun next month, following a court ruling that threw the entire polling process into confusion.
The stadium riot took place last year at the end of a match in Port Said between local side Al-Masry and Cairo's Al-Ahly team.
Spectators were crushed when panicked crowds tried to escape from the stadium after a pitch invasion by Al-Masry supporters.
Others fell or were thrown from terraces.
Judge Sobhy Abdel Maguid, listing the names of the 21 Al-Masry fans, said the Cairo court had confirmed "the death penalty by hanging".
He also sentenced five more people to life imprisonment while others out of a total of 73 defendants received shorter terms.
In Cairo, local Al-Ahly fans vented their rage at the acquittals, setting fire to a police social club, the nearby offices of the Egyptian soccer federation and a branch of a fast food chain, sending smoke rising over the capital.
In Port Said, where the army took over security in the city centre from the police yesterday, about 2,000 residents who want the local fans spared from execution blockaded ferries crossing the Suez Canal.
Authorities controlling the Canal, an artery for global trade and major income source for the Egyptian government, said through traffic had not been affected.