Charlotte: Video shows protester shot in head during violent demonstrations over police killing of Keith Lamont Scott

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A protester is on life support after being shot in the head during protests following the police killing of a black man in North Carolina.

A peaceful demonstration deteriorated into a night of violence in the city of Charlotte on Wednesday night, were authorities declared a state of emergency as police cracked down on hundreds of protesters.

As demonstrators clashed with lines of riot police outside the Omni Hotel in the city centre, a loud bang was heard and people started to run screaming from the scene.

Seriously wounded man carried into Omni Hotel during second day of Charlotte protests <em>Brian Blanco/Getty Images</em>

Footage recorded immediately afterwards showed a black man lying in a pool of blood as people shouted for help before being ordered to move back by police.

Witnesses he had been shot in the head but there were conflicting reports of whether a gun, rubber bullet or tear gas was used, and whether it was fired by police or other demonstrators.

Gloria Merriweather, a young black woman, spoke to the Associated Press while shaking and trying to hold back tears.

“We were walking by…and they started shooting bullets at us and throwing tear gas and this guy got hit and they wouldn’t let us move him,” she said.

“He got hit in the head. The whole reason we had to protest is because somebody was shot, unarmed, and another unarmed person is shot today.”

It was unclear whether Ms Merriweather was referring to rubber bullets or live ammunition.

Writing in the Daily Beast, a witness called Ryan James said he watched a civilian "fire a pistol indiscriminately" into the crowd at around 8.30pm local time.

"Standing about 10 yards away, I looked down the barrel of a pistol...the bullet had whizzed past me," he wrote. "The shooter, a black male, was standing at the intersection of East Trade and South College streets with the weapon still aimed. He turned and ran."

The City of Charlotte council sent out a message shortly after the incident saying the man had been fatally shot in a “civilian on civilian shooting”.

But a correction was swiftly issued saying the man had not died and was on life support in hospital, where he was in a critical condition.

Officials said police were not responsible for the shooting but protesters doubted the claim. “We protesting. Why the hell would we target each other?” Dino Davis asked.

“They say it was the tear gas, and it looked like one the tear gas exploded. But I think it was a rubber bullet because some of those rubber bullets can penetrate.”

Pat McCrory, the governor of North Carolina, declared a state of emergency overnight in the state's largest city and called in the National Guard after Charlotte's police chief said he needed help.

A peaceful prayer vigil turned into an angry march, with hundreds of protesters shouting shouting “black lives matter” and “hands up, don't shoot” met by volleys of tear gas and stun grenades by police.

But several groups of a dozen or more protesters stayed behind, attacking people, including reporters, shattering windows to hotels, office buildings and restaurants and starting small fires.

A reporter and cameraman for the local WCNC-TV were taken to hospital and a CNN journalist was pushed to the ground live on television.

Authorities said three people and four police officers were injured, but the figures are expected to rise.

(Getty Images (Getty Images)

The protests were sparked by the police shooting of 43-year-old Keith Lamont Scott on Tuesday.

He was killed in the car park of his condominium complex, with officials and friends and family offering conflicting accounts of events.

Police did not release dashboard or body camera footage but insisted Mr Scott had a gun and refused several orders to drop his weapon. But his family and neighbours said he was holding a book.

Charlotte Police Chief Kerr Putney was adamant that Mr Scott posed a threat, even if he didn't point his weapon at officers, and said a gun was found next to the dead man.

“I can tell you we did not find a book,” he said.

Wednesday was the second night of protests over the shooting, the latest in a series of controversial police killings of black men in the US, with protests erupting near the scene of Mr Scott’s death on Tuesday.

Additional reporting by AP