Police officers wearing riot gear block a road during protests after police fatally shot Keith Lamont Scott in the parking lot of an apartment complex in Charlotte, North Carolina, US September 20, 2016. [Photo/Agencies]

Widely differing accounts of Tuesday's shooting emerged the next day. Police said Keith Scott, 43, was armed and ignoring officers' orders when he was gunned down, while the victim's family and a witness said he was holding a book, not a weapon.

Authorities have not released any video of the incident, but the city's mayor said they plan to.

Scott's wife, Rakeyia, issued a statement describing her family as "devastated" and appealing for calm, adding, "we have more questions than answers about Keith's death."

Tuesday's disturbances in Charlotte unfolded as demonstrators in Tulsa, Oklahoma, demanded the arrest of a police officer seen in video last week fatally shooting an unarmed black man who had his hands in clear view at the time.

The deaths were the latest incidents to raise questions of racial bias in US law enforcement, and they stoked a national debate on policing ahead of the presidential election in November. President Barack Obama spoke by telephone on Wednesday with the mayors of Charlotte and Tulsa, a White House official said.