The sacked police officer whose fatal knee-on-neck arrest of George Floyd sparked blazing riots in Minneapolis has been charged with murder and manslaughter.

Derek Chauvin, 44, was filmed kneeling on Floyd as the unarmed and handcuffed African American gasped and pleaded “Please, I can’t breathe”. The man died shortly afterwards.

The white officer had his knee on Floyd’s neck for eight minutes and 46 seconds, including nearly three minutes after Floyd stopped moving and talking, according to details of the criminal complaint.

The White House was been sent into temporary lockdown as protests in the national capital escalated.

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Chauvin, who was later sacked alongside three other officers, has been charged with third-degree murder and second-degree manslaughter as outlined by Hennepin County attorney Mike Freeman at a news briefing.

Derek Chauvin, the former Minneapolis police officer seen in a video with his knee on George Floyd's neck, has been arrested and faces charges of third-degree murder and manslaughter, according to Hennepin County Attorney Mike Freeman https://t.co/cCSZyGMZj4 pic.twitter.com/Lt8LGk85YG

— CNN (@CNN) May 29, 2020

The criminal complaint said an autopsy found nothing to support strangulation, with the medical examiner concluding a combination of being restrained, potential intoxicants in Floyd’s system and his underlying health issues likely contributed to his death.

Chauvin is accused of ignoring another policeman who was worried the handcuffed man should be rolled onto his side.

The complaint said Floyd was struggling with officers who tried to put him in a squad car and at one point he went to the ground face down.

One officer held Floyd’s back and another held his legs, while Chauvin put his knee on Floyd’s head and neck area.

Video of George Floyd pinned by his neck has been cited as part of the evidence leading to a murder charge.

When one officer said he was getting worried and asked if Floyd should be rolled onto his side, Chauvin said no, the complaint states.

“We are continuing to review the evidence; there may be subsequent charges later,” Mr Freeman said.

“We have evidence. We have the citizen’s camera, video – the horrible, horrific, terrible thing we’ve all seen over and over again.

“We have the officer’s body-worn camera, we have statements from some witnesses, we have a preliminary report from the medical examiner. We have discussions with an expert.

“All of that has come together so we felt in our professional judgement it was time to charge.”

George Floyd was unarmed when he was arrested over suspicions he had used counterfeit money at an eatery.

It comes after a third night of violent protests in the US mid-western city in which protesters torched a police station that officers abandoned and Donald Trump called in the National Guard.

Police evacuated the 3rd Precinct station, the focus of many of the protests, late on Thursday to protect employees, a spokesman said.

Dozens of fires were also set in nearby St Paul, where nearly 200 businesses were damaged or looted and a building collapsed in flames.

Protesters gather in front of a liquor store in flames. Photo: Getty

The protests fuelled by outrage over Floyd’s death and police treatment of African Americans have spread across America, with demonstrators clashing with officers in New York and blocking traffic in Columbus, Ohio and Denver.

President Donald Trump reacted to the unfolding racial tensions by threatening to bring Minneapolis “under control,” calling the rioters “thugs” and tweeting that “when the looting starts, the shooting starts” which drew a warning from Twitter.

Chauvin has been charged with the same murder and manslaughter counts as the officer convicted of shooting dead Australian life coach Justine Ruszczyk Damond.

Mr Freeman repeatedly referred to his successful prosecution last year of Mohamed Noor, the Minneapolis police officer.

“The Hennepin County Attorney’s office is one of the few prosecuting offices in this country in the last five years to successfully prosecute a police officer for murder and we did that on behalf of Justine Damond,” Mr Freeman said.

“That’s unusual.

“We know how to do this.”

Protests have been escalating for three nights. Photo: Getty

Minneapolis Mayor Jacob Frey said there was “a lot of pain and anger right now in our city” but warned against criminal behaviour.

“What we have seen over the past several hours and past couple of nights here in terms of looting is unacceptable,” said Cr Frey.

He defended the fact there had been only a handful of arrests across the first two nights of violence, saying, “we are doing absolutely everything that we can to keep the peace.”

Cr Frey said the National Guard was stationed in locations to help stem looting, including at banks, grocery stores and pharmacies.

Meanwhile the Minnesota State Patrol said a CNN television crew was among four people arrested as troopers were “clearing the streets and restoring order,” but they were released after being confirmed to be media members.

CNN said on Twitter that the arrests were “a clear violation of their First Amendment rights”.

The eruption of rage has been fuelled in part by local media reports that the police officer had 18 prior complaints filed against him with the Minneapolis Police Department’s Internal Affairs unit.

One of those incidents led to charges which came to nothing when prosecutors declined to proceed.

St. Paul Police Chief Todd Axtell said the scale of looting was unlike anything he’d seen in a 32-year career.

“We are going to hold offenders accountable, whether that’s today or down the road in the future,” he promised.

-with AAP