Two former Minneapolis police officers were sentenced on federal charges on Wednesday for their roles in the May 2020 killing of George Floyd, the African American man whose death sparked protests against racial injustice across the United States.

U.S. District Judge Paul Magnuson sentenced J. Alexander Kueng, 28, to three years in prison, and 36-year-old Tou Thao to three and a half years.

Kueng and Thao were convicted in February of violating Floyd's civil rights, showing "deliberate indifference" to his medical needs and failing to intervene to stop the use of "unreasonable force" by another officer, Derek Chauvin.

Kueng, Thao and Chauvin were among four police officers involved in Floyd's arrest for allegedly using a counterfeit US$20 bill to buy a pack of cigarettes.

Chauvin, a 19-year veteran of the force who kneeled on the neck of a handcuffed Floyd for nearly 10 minutes until he passed out and died, was convicted of murder and is serving more than 20 years in prison.

The fourth officer, Thomas Lane, was convicted in February of violating Floyd's civil rights and sentenced to two and a half years in prison.

Lane's lawyers had asked for a lighter sentence for him on the grounds that he had suggested placing Floyd on his side and tried to resuscitate him.

Kueng and Lane helped to restrain Floyd while Thao kept away bystanders who were pleading with the officers to get off of Floyd as he lay face down on the ground complaining he could not breathe.

Lane was new to the job when he and fellow rookie cop Kueng apprehended Floyd after a shopkeeper accused him of using a counterfeit bill in his store.

As they struggled to get Floyd into their vehicle, the pair were joined by two experienced officers, Chauvin and Thao.

Lane pleaded guilty in May to separate state charges of aiding and abetting second-degree manslaughter, under a plea agreement that will see him spend three years in jail.

Kueng and Thao are to go on trial on state manslaughter charges in late October.