Prosecutors plan to charge a Minneapolis police officer accused of pressing his knee against George Floyd’s neck with second-degree murder, and for the first time will level charges against three other officers at the scene, a newspaper has reported.

Widely seen bystander video showing Mr Floyd’s May 25 death has sparked protests nationwide and around the world.

The officer, Derek Chauvin, was fired on May 26 and initially charged with third-degree murder and second-degree manslaughter. The three other officers were also fired but were not immediately charged.

The Star Tribune reported that Minnesota Attorney General Keith Ellison would be upgrading the charge against Chauvin while also charging Thomas Lane, J Kueng and Tou Thao with aiding and abetting second-degree murder.

The newspaper cited multiple law enforcement sources familiar with the case who spoke on condition of anonymity.

Minnesota Attorney General Keith Ellison. Credit: John Autey/Pioneer Press via AP, Pool, File

Mr Ellison planned an announcement later on Wednesday on the case, but his office did not respond to questions about the Star Tribune report.

Lawyer Earl Gray, who represents Lane, told The Associated Press that the report “is accurate” before ending the call.

Before news of the upgraded charges, a lawyer for Chauvin said he was not making any statements at this time. Lawyers for Thao and Kueng did not return messages seeking comment on the charges.

Lawyer Ben Crump tweeted that the Floyd family was “deeply gratified” by Mr Ellison’s action and called it “a source of peace for George’s family in this difficult time”.

He said Mr Ellison had told the family his office will continue to investigate and upgrade charges against Chauvin to first-degree murder if warranted.

Reached by phone, Mr Crump declined to speak beyond the statement or make clear when Mr Ellison had spoken with the family and whether he had been informed directly that additional charges had been filed.

Mr Floyd’s family and protesters have repeatedly called for criminal charges against all four officers as well as more serious charges for Chauvin, who held his knee to Mr Floyd’s neck.

A portrait of George Floyd in a memorial for him in Minneapolis. Credit: Jim Mone/AP

Some of the rockiness of the days since Mr Floyd’s death May 25 dissipated on Tuesday night, with demonstrations continuing around the country, but without major reports of violence.

Curfews and efforts by protesters to contain earlier flare-ups of lawlessness were credited with preventing more widespread damage to businesses in New York and other cities overnight.

“Last night we took a step forward in moving out of this difficult period we’ve had the last few days and moving to a better time,” New York mayor Bill de Blasio said.

New York police said they arrested about 280 people on protest-related charges on Tuesday night, compared with 700 a day earlier.

Nationwide, the number arrested in connection to the unrest rose to more than 9,000.

At least 12 deaths have been reported, though the circumstances in many cases are still being sorted out.

Some tense incidents continued Tuesday night, but were far less prevalent than in preceding days.

Police and National Guard troops used tear gas, flash-bang grenades, nonlethal rounds and other means of dispersing crowds near a police precinct in Seattle, near Centennial Park in Atlanta and at demonstrations in Tampa and St Petersburg, Florida.