The main security building in Egypt's Port Said was set ablaze on Monday, as fighting which cost six lives erupted anew between police and protesters in the restive Suez Canal city, AFP reported.
According to the report the blaze, which started on the ground floor of the security headquarters, sent plumes of smoke into the air while clashes continued in the streets surrounding the building.
Rescue services could not reach the area, witnesses said, as anger mounted in the city where a campaign of civil disobedience entered its third week.
The interior ministry said in a statement quoted by AFP that unknown assailants had randomly attacked police and army personnel in the city "with the aim of creating sedition and divisions" between them.
It urged residents of Port Said "to stay away from groupings near government buildings," reported AFP.
Earlier, thousands had taken to the streets for the funeral of the three civilians killed in the overnight clashes, chanting against the police and Islamist President Mohammed Morsi.
"The interior ministry (officials) are cowards!" the angry mourners chanted, and called on Morsi to "leave."
Aside from those killed, hundreds were injured in the overnight fighting after the authorities decided to move prisoners awaiting a verdict over alleged involvement in a deadly soccer riot last year.
Two policemen died from gunshots to the head and neck and a third died of his wounds later on Monday, the interior ministry said.
Of the 586 people injured in the confrontations, 16 had been hit with live rounds and 27 with birdshot, according to Ahmed Sultan, head of emergency services.
A security official said that during the night protesters threw petrol bombs and stones at the police station in Port Said, where a general strike entered its third week, and the police responded with tear gas.
The city has witnessed unrest since January when a court sentenced Port Said residents to death over a football stadium riot last year, triggering a series of protests and eventually a civil disobedience campaign.
Traffic in the Suez Canal, a vital waterway for global commerce, has not been disrupted, the canal authority said.
The interior ministry said it decided to move the prisoners from Port Said because it wanted to avoid unrest.
The court verdict, expected on Saturday, is for 39 defendants in a case which has already resulted in death sentences for 21 others, sparking clashes that killed at least 40 people.
In Cairo, dozens of youths hurled stones at public buses, AFP reported. A police car was set ablaze near Tahrir Square, with protesters blocking access to ambulance and fire services.
Amid the security and economic mayhem in the country, leading opposition figure Amr Moussa called on Twitter for a postponement of Egypt's parliamentary elections which are due to start in April.
"A delay to the elections is the solution," he wrote, according to AFP.
Egypt has been gripped by nationwide unrest in the past few months, with protesters taking to the streets to denounce Morsi for failing to address political and economic concerns.
Opponents accuse Morsi of failing the revolution that brought him to the presidency and of consolidating power in the hands of his Muslim Brotherhood movement.