Police here in the US city of Cleveland shot and killed a 12-year-old boy who was in a playground waving around what turned out to be a replica gun, officials and reports said on Sunday.

The shooting comes as a grand jury was set to announce if a white policeman will be indicted for the fatal shooting of an unarmed black teenager in the St Louis suburb of Ferguson in Missouri, an incident that has prompted months of protests and violence.

Officers called to the scene in Cleveland on Saturday fired at the boy twice, hitting him at least once in the stomach, after reports that he was pointing a gun at people.

He died early on Sunday Cleveland's newspaper The Plain Dealer reported.

One of the police officers was in his first year in the force, the newspaper said.

Audio released of a 911 call made to police details the caller saying the gun was "probably fake".

The man told 911 that he could see "a guy with a pistol" on the swing set who was pulling the weapon from his pants and scaring the s--- out of everyone", according to the Plain Dealer.

A Cleveland police statement said: "Upon arrival on scene, officers located the suspect and advised him to raise his hands. The suspect did not comply with the officers' orders and reached to his waistband for the gun.

"Shots were fired and the suspect was struck in the torso."

According to AFP, the report added: "Further information reveals that the weapon which the 12-year-old suspect was in possession of is an 'airsoft' type replica gun resembling a semi-automatic pistol, with the orange safety indicator removed."

The victim has not been named.