Egypt's military intervened in clashes between thousands of protesters and police in the restive Suez Canal city of Port Said in the early hours today.
Around 5,000 protesters threw rocks and firebombs at police, continuing a street-level revolt now in its second week.
Riot police responded with tear gas and birdshot in battles that lasted for hours.
The fight outside police and government buildings started early on Sunday and continued until past midnight.
At one point Egyptian soldiers intervened by forming a line between the two sides, as protesters climbed the tanks chanting support for the country's armed forces that unlike the police have not cracked down on rioters in the city.
"The people and the army are one hand!" the demonstrators shouted, urging the soldiers to side with them.
But a military spokesman denied that soldiers had been firing at the police.
"The armed forces are on the scene to protect the government building and to separate the protesters and interior ministry force," military spokesman Ahmed Mohammed Ali said.
Health official Helmy el-Afani said that 325 people had been injured in the clashes.
Most suffered tear gas inhalation and some were wounded by birdshot.
The Interior Ministry said one policeman had been killed by gunfire and that one soldier and at least 10 policemen had been wounded.
A medical official later said that one of the wounded policemen died of his wounds and two civilians had been killed.
Port Said residents are demanding retribution for excessive police force that led to the deaths of more than 40 civilians in late January.
Sunday was the first time the army had intervened between police and protesters in Port Said since the military was put in charge of securing the city in late January. The police had all but disappeared since.
Protests swept the city on January 26 after a Cairo court issued death sentences against 21 people, most from Port Said, for their part in Egypt's deadliest football riot in February 2012.
A March 9 hearing is expected to issue verdicts on police officers and the remaining defendants.