Derek Chauvin, the former Minneapolis police officer convicted in the death of George Floyd, was attacked in a prison in Arizona, Minnesota Attorney General Keith Ellison has confirmed.
The Associated Press had earlier reported Chauvin had been stabbed and seriously injured yesterday.
"I am sad to hear that Derek Chauvin was the target of violence," Attorney General Ellison said in an emailed statement.
"He was duly convicted of his crimes and, like any incarcerated individual, he should be able to serve his sentence without fear of retaliation or violence."
He did not give further details.
Chauvin is serving a 21-year federal sentence for violating Mr Floyd's civil rights, as well as a concurrent 22-and-a-half years for murder on his conviction in Minnesota state court.
The Federal Bureau of Prisons confirmed an unidentified inmate was assaulted at the Federal Correctional Institution in Tucson, Arizona.
It said employees "initiated life-saving measures" for one individual, who was taken by emergency medical services to a hospital.
George Floyd's death in 2020 unleashed protests worldwide against police brutality and racism after Chauvin, who is white, knelt on the neck of the handcuffed Black man for more than nine minutes in a murder caught on mobile phone footage.
On Monday, the US Supreme Court declined to hear Chauvin's appeal of his state court murder conviction. The appeal had been filed after a Minnesota appellate court upheld his 2021 murder conviction and rejected his request for a new trial.
Chauvin had said jury bias and some rulings by the presiding judge deprived him of his right to a fair trial.
Chauvin was helping three fellow officers to arrest Mr Floyd in May 2020 on suspicion that Mr Floyd had used a fake $20 bill when buying cigarettes.
The three – Tou Thao, J. Alexander Keung and Thomas Lane –have been convicted of lesser state and federal charges.
