A white US police officer has shot and killed a 13-year-old black boy in the state of Ohio while chasing down suspects of a reported robbery, after the teenager allegedly pulled out a pellet gun.

Police in the town of Columbus, where the incident took place, said they were investigating Wednesday's killing of Tyre King, the latest in a string of shootings of African Americans by law enforcement officers that have fuelled protests and national debate about policing tactics in US cities.

"We got a call on 911 saying that an armed robbery was being reported," police chief Kim Jacobs said at a news conference on Thursday.

"Once they [officers] arrived at that scene they saw some people that they believed matched the description of the suspects and tried to track down those suspects.

"A confrontation happened and there was a policeman involved in shooting," said Jacobs, adding that "one of the officers fired and as result of that the young man succumbed to his injuries".

Police said King was shot multiple times after he pulled out a BB gun - a low-powered air gun which shoots small round pellets - during the confrontation, and was later pronounced dead at Nationwide Children's Hospital.

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Police promised to investigate the case "thoroughly", but lawyers for King's family called for an independent investigation, saying some witness accounts conflicted with the police version of what happened, according to the Associated Press news agency. 

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The lawyers said allegations about King cannot be considered fact until there's a "thorough, unbiased investigation".

Sean Walton, an attorney for King's family, said the eighth-grader had no violent criminal history. He said King played football and was in the young scholars programme at school.

Walton also quoted the boy's family as saying involvement in an armed robbery would be "so out of character" for King.

At the police news conference, Jacobs displayed a photo of a BB gun like the one King allegedly had.

"Officers carry a gun that looks practically identical to this weapon," he said. "It turned out to not be a firearm ... that fires real bullets. But as you can see, it looks like a firearm that could kill you."

BB guns have small ball munitions, typically made of steel with copper or zinc coating.

The officer who shot him was identified as Bryan Mason, a white, nine-year veteran of the department who had recently been assigned to the neighbourhood where the incident took place.

Police records show that in 2012 he shot and killed a man who was holding another person at gunpoint, according to AP. The Columbus Dispatch said investigators cleared him.

The case has brought comparisons with the 2014 killing in the city of Cleveland of 12-year-old Tamir Rice, who was shot dead by a white police officer while playing with a pellet gun outside a recreation centre.

'There is something wrong in this country'

More than 150 people, including some of King's family members, gathered for a prayer vigil on Thursday near where he was shot, the Columbus Dispatch reported.

On Thursday morning, Mayor Andrew Ginther appeared to choke up as he called for the community to come together and questioned why an eighth-grader would have a replica of a police firearm.

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"There is something wrong in this country, and it is bringing its epidemic to our city streets," Ginther said.

"And a 13-year-old is dead in the city of Columbus because of our obsession with guns and violence."

Dozens of people attended a Thursday evening vigil near the scene of the shooting.

Some carried signs calling for justice for Tyre. Among those participating were several members of Tyre's youth football team.

The second male who ran into the alley was interviewed by police and released.

The Columbus Dispatch newspaper identified the second male as Demetrius Braxton, 19, who told the newspaper in an interview that he was with King for both the robbery and the shooting.

"I was in the situation. We robbed somebody, the people I was with," Braxton said, according to the Dispatch.

Braxton told the paper that, following the robbery, the suspects were chased by police."

The cops said to get down. We got down but my friend [King] got up and ran," Braxton said. "He started to run. When he ran, the cops shot him."

Braxton told the paper that King was shot four or five times, asking "Why didn't they tase him?"

A grand jury will ultimately decide whether the officer should face criminal charges, police chief Jacobs said.

Source: News Agencies