Thousands of Egyptian protesters have blocked access to the harbour and rallied outside state buildings in Port Said to demand justice over the deaths of dozens of people killed in riots last month.
The violence on Sunday was triggered by anger over the death sentences handed down to 21 people from Port Said for their involvement in a soccer stadium disaster in the city a year ago in which more than 70 people were killed.
The verdict enraged people in Port Said, where the majority of the condemned were local soccer fans, many of whom claim innocence.
Sunday's day of "civil disobedience" was called by hardcore football supporters of Port Said's al-Masry, the club that had been playing a home match against Cairo's Al Ahly when the stadium disaster occurred in February 2012.
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Al Jazeera's Rawya Rageh, reporting from Cairo, said that the protest was aimed at "bringing the city to a complete standstill".
"A few thousand marched through Port Said, laying siege to key government buildings, including city hall, the port authority, the industrial zone and parts of the railway tracks," said Rageh.
Witnesses said around 3,000 people took part in the protest, demanding the death sentence for those responsible for the January 26 violence set off by a verdict read out in Cairo.
"With our lives, with our blood, we will sacrifice ourselves to you martyrs: Either we avenge you or we die like you!" they chanted.
"The disobedience will last for one day and could continue if the protesters' calls for the death sentence for the killers
of martyrs are not granted," said Ahmad Mutwalli, a political activist in Port Said.
The protesters also disrupted train services.
General Ahmed Najeeb, head of the General Authority of Port Said, said the protest had not affected shipping activity at the Mediterranean port.
Port Said was one of three provinces near the Suez Canal where President Mohamed Mursi declared a 30-day state of emergency in response to last month's unrest.