The charred carcasses of vehicles blocked a main road of the capital and in some slum neighborhoods, residents locked their doors as pro-Aristide militants shot at police from behind the wreckage.

It was unclear if anyone was wounded or killed in Thursday's violence. But along Port-au-Prince's seaside road, gunfire was reported and people told a radio station that four people were killed by armed civilians. The reports could not be independently confirmed.

The surge in violence marks growing chaos in Haiti and an increasingly difficult challenge for a U.S.-backed interim government that has promised elections next year. A month of violence has left at least 62 people dead - not including the 13 people residents said were executed by police on Tuesday.

People who said they were witnesses and relatives of the victims described the police executions, while occasional gunshots whizzed around Fort National, a warren of alleyways and one-room homes in the capital. Police and interim Prime Minister Gerard Latortue denied residents' accusations.

''I was on the roof taking clothes off the line when my friend Reginald was trying to run away from [the police],'' said Renemise Joseph, 23. ''They shot him in the mouth. Then they dragged him away and I heard another shot. We couldn't see anything else because when they arrived they shouted: 'Everybody get down, get down.' ''