Four people including two policemen were killed in overnight clashes between security forces and protesters in Egypt's restive canal city of Port Said, the interior ministry said on Monday.
At least 420 people were also injured in the clashes which began on Sunday after authorities decided to move prisoners awaiting a verdict over alleged involvement in a deadly football riot last year.
The two policemen died from gunshots to the head and neck, an interior ministry official said.
A security official said earlier that protesters threw petrol bombs and stones at the police station in Port Said, where a general strike entered its third week. Police responded with tear gas.
The interior ministry said it decided to move prisoners from Port Said, starting with the 39 remaining defendants over the February 2012 football violence, because it wanted to avoid unrest.
The court verdict, expected next Saturday, is for the 39 defendants in a case which resulted in death sentences in January for 21 other defendants, sparking clashes that killed at least 40 people.
Residents of Port Said and other canal cities have long complained that Cairo marginalises them.
Last year's football riot which killed 74 people, mostly supporters of a visiting Cairo team, exacerbated Port Said's isolation, residents of the city say.
Overnight clashes also erupted in Cairo between police and protesters near Tahrir Square.
Police fired tear gas to disperse the crowd as they approached a luxury hotel on the banks of the Nile which was damaged in clashes last month, a security official said.
Officials say calm has been restored to the area.
Egypt has been gripped by nationwide unrest in recent months, with protesters taking to the streets to denounce Islamist President Mohamed Morsi for failing to address political and economic concerns.
Opponents accuse Morsi -- elected in June last year after a turbulent period of military rule -- of failing the revolution that brought him to the presidency and of consolidating power in the hands of his Muslim Brotherhood movement.
The Nile Delta has also seen its share of unrest, with a civil disobedience campaign declared in the province of Daqahliyah.
One person was killed and dozens injured in clashes over the weekend between police and protesters in Mansura, the province capital.