MINNEAPOLIS: A Minneapolis curfew was set to begin Monday after a police officer fatally shot a young Black man when she confused her handgun with her taser, fueling tensions in a US city already on edge because of the George Floyd murder trial.

In police body camera video released in Brooklyn Center where Sunday's killing occurred, an officer shouts "Taser! Taser! Taser!" but then instead fires a gun at the victim, 20-year-old Daunte Wright.

"The officer drew their handgun instead of their taser," Brooklyn Center police chief Tim Gannon told a press conference.

Gannon said it was his belief that the officer, now on leave pending an investigation, "had the intention to deploy their taser but instead shot Mr Wright with a single bullet."

"This was an accidental discharge that resulted in the tragic death of Mr Wright," Gannon said. "There is nothing I can say to lessen the pain of Mr Wright's family."

Wright's killing sparked protests overnight in Brooklyn Center and the looting of a shopping mall, and authorities in Minneapolis, and surrounding suburbs including Brooklyn Center announced a curfew from 7:00 pm (0000 GMT) Monday until 6:00 am Tuesday.

In the body cam footage, police officers are seen pulling Wright out of his car after stopping him for a traffic violation and discovering he had an outstanding warrant.

When officers attempt to handcuff Wright he scuffles with them and gets back in the car. A female police officer shouts "I'll tase you" and then "Taser! Taser! Taser!" - standard police procedure before an officer fires one of the stun guns.

"Holy shit, I shot him," the officer says as Wright, fatally wounded, drives off. He crashed his car a few blocks away.

How the officer mistook her gun for a taser was unclear.

Gannon said police are trained to place handguns "on our dominant side, and our taser on our weak side."

President Joe Biden called the killing "tragic," but warned against any potential violent unrest.

"I think we have to wait and see what the investigation shows," Biden told reporters.

"In the meantime, I want to make it clear again: there is absolutely no justification, none, for looting," he added. "Peaceful protests - understandable."

The protests overnight prompted the defense attorney for former officer Derek Chauvin, who is facing murder and manslaughter charges for George Floyd's death, to ask the judge presiding over the high-profile case to sequester the jury.

Judge Peter Cahill refused, stating "this is a totally different case."

'Tragic events'

Chauvin is facing murder and manslaughter charges for his role in Floyd's death on May 25, 2020, which occurred during his arrest for allegedly passing a fake $20 bill.

The 45-year-old Chauvin, who is white, was seen in a video taken by a bystander kneeling on Floyd's neck for more than nine minutes as the handcuffed 46-year-old Black man complained repeatedly that he could not breathe.

The video touched off protests against racial injustice and police brutality in the United States and around the world.

Brooklyn Center, where Wright was shot, is a northwest suburb of Minneapolis located not far from the heavily guarded Hennepin County Government Center where Chauvin is on trial.

Officers fired tear gas and flash bangs to disperse a crowd of hundreds who gathered outside a police station in Brooklyn Center after Wright was shot. National Guard troops were deployed.

"We are in pain right now, and we recognize that this couldn't have happened at a worse time," Brooklyn Center Mayor Mike Elliott said.

The Minnesota Twins announced they were postponing their Monday baseball game against the Boston Red Sox "out of respect for the tragic events that occurred yesterday in Brooklyn Center."

The US professional basketball and hockey leagues also postponed their Monday games involving Minnesota teams.

Tensions in Minneapolis are already high over Chauvin's trial.

Prosecutors are seeking to prove Floyd's death was due to asphyxiation by the officers conducting the arrest and have called several medical experts to bolster their case.

Chauvin's attorney claims Floyd's death was due to his consumption of the illegal drugs fentanyl and methamphetamine and underlying health conditions.

Prosecutors called a prominent cardiologist, Jonathan Rich, to testify on Monday.

Rich said Floyd's death was caused by "low oxygen levels" that were "induced by the prone restraint and positional asphyxiation that he was subjected to."

"I see no evidence at all that a fentanyl overdose caused Mr Floyd's death," Rich said.

Also testifying was an ex-police officer and law professor, Seth Stoughton, who said he found the force used against Floyd to be "excessive."

"The knee across Mr Floyd's neck and the prone restraint were unreasonable," Stoughton said. "No reasonable officer would believe that was an appropriate, acceptable or reasonable use of force."

Floyd's brother, Philonise Floyd, 39, also took the witness stand and emotionally recounted stories from their childhood.

Judge Cahill told jurors before dismissing them for the day that he expected Chauvin's defense to begin its presentation Tuesday. –AFP