The Ohio city of Akron has declared a state of emergency, setting a curfew and cancelling Independence Day fireworks, after protests over the police killing of an unarmed black man turned unruly on Sunday night.

The protests broke out after police released body camera video that showed eight officers shooting at 25-year-old Jayland Walker as he fled a traffic stop last week.

Mr Walker's body was found to have some 60 gunshot wounds.

Daytime protests yesterday were peaceful but, despite pleas from the Walker family that demonstrations remain peaceful, Akron police declared an unlawful assembly once property was damaged. Officers in riot gear fired about a dozen canisters of tear gas to scatter protesters, local media outlet WKYC-TV said.

Akron Mayor Dan Horrigan said a curfew for downtown Akron was in effect from 9pm to 6am until further notice, and a pair of Fourth of July fireworks displays also were cancelled.

"There was significant property damage done to downtown Akron. Small businesses up and down Main Street have had their windows broken. We cannot and will not tolerate the destruction of property or violence," Mr Horrigan said in a statement.

The officers said they had believed Mr Walker was 'moving into firing position' when he got out of his car

Police said Mr Walker had a gun in his car but left it on the front seat as he fled on foot. Officers believed he fired a round from inside the car before fleeing, police said, and that Mr Walker was "moving into firing position" when he got out of his car, prompting them to react to him as a potential threat, Akron Police Chief Stephen Mylett said.

The mayor praised the peaceful protests, which were led by the Akron chapter of the NAACP.

Hundreds of demonstrators marched in the streets of the city of about 200,000 people, waving "Black Lives Matter" flags and chanting, "We are done dying," and "Justice for Jayland".

Mr Horrigan said the trouble began after nightfall, a pattern that was seen in the turbulent summer of 2020 when protests spread across the United States over the death of George Floyd, a black man who died when a white Minneapolis police officer kneeled on his neck for several minutes. Officers were later convicted of various charges including murder and civil rights violations in the Floyd case.

The attorney for the Walker family, Bobby DiCello, told reporters he was "very concerned" about the police accusation that Mr Walker had fired at officers from his car, adding that there was no justification for his violent death.

"I ask you, as he's running away, what is reasonable? To gun him down? No, that's not reasonable," Mr DiCello said.

The Ohio attorney general and Ohio's Bureau of Criminal Investigation are investigating, and the file will be made public at the conclusion of the case, Attorney General Dave Yost said on Sunday.

"People want and deserve answers, and they shall have them," Mr Yost said in a statement

The eight officers directly involved in the shooting have been placed on paid administrative leave, the Akron police chief said.