The governor of North Carolina has declared a state of emergency in the city of Charlotte, sending in the National Guard, as unrest over a police shooting continues.

Violence erupted for a second night as protests over the killing of a black man spun out of control.

One protester is in a critical condition after a "civilian on civilian" incident, the city said.

Riot police used tear gas as they faced hundreds of protesters.

The demonstrators are angry that Keith Lamont Scott, 43, was killed by police on Tuesday.

Police say Mr Scott was repeatedly told to drop his handgun before he was shot but his family say he was reading a book at the time.

Sixteen police officers were injured in unrest on Tuesday night.

Bottles and fireworks

Governor Pat McCrory declared the state of emergency as rioters attacked journalists and other people, breaking windows and setting small fires.

The second night of protests had begun peacefully but the demonstration was interrupted by gunfire and a man in the crowd was injured. The city initially said he had been killed but then issued a clarification on Twitter.

Protesters then threw bottles and fireworks at the officers, who were lined up in riot gear. Police fired flash grenades and tear gas to repel the crowds.

The use of lethal police force against African Americans has been the subject of nationwide protests across the US for two years.

Three fatal police shootings in last week

a boy, 13, shot dead in Ohio after allegedly pulling an air gun from his waistband during arrest

an unarmed, stranded motorist was killed in Tulsa, Oklahoma, in what Donald Trump described as a "troubling" incident

Keith Lamont Scott shot in Charlotte and died in hospitalAnother African American, Terence Crutcher, was killed by police in Tulsa on Friday, and officers said on Sunday he had been unarmed.

Police in Charlotte on Wednesday appealed for calm and defended their actions in the death of Mr Scott by insisting he had been repeatedly warned to drop his gun.

Charlotte-Mecklenburg Police Chief Kerr Putney told a news conference Mr Scott first got out of the car with a gun, then got back into his vehicle when officers told him to drop his weapon.

He was shot when he emerged from his car holding his weapon. The police chief was unable to say if Mr Scott had been pointing his weapon at officers.

After her father's death, Mr Scott's daughter posted a video on Facebook in which she said her father had been unarmed and reading a book as he waited for the school bus to drop off his son, when he was shot.

The mayor of Charlotte, Jennifer Robert, voiced her shock at the violent protests.

"Charlotte is a city that has worked very hard to build good community police relations," she told the BBC.

"We have been a model of community policing. We have actually trained other police forces. This is not who we are as Charlotteans and I'm hoping we can move past these protests very quickly, move into more peaceful protests and back into dialogue."