A US state governor on Thursday postponed the scheduled execution of Keith LaMar, whose campaign against a three-decade-old death sentence has won the backing of a jazz group, until January 2027 due to issues procuring the lethal injection.

On death row in the midwest state of Ohio, LaMar was convicted of killing five fellow inmates during an 11-day prison riot in 1993.

The 54-year-old maintains he had nothing to do with the deaths and has called for his case to be reexamined, alleging that important evidence had been destroyed and information had been withheld at the time.

Ohio Governor Mike DeWine, a Republican, issued the reprieve "due to ongoing problems involving the willingness of pharmaceutical suppliers to provide drugs" for executions, his office said in a statement.

DeWine had issued similar reprieves in recent years due to the same issue. The state has not carried out an execution since 2018, according to the Death Penalty Information Center.

LaMar has been in jail since he was 19 years old, after pleading guilty to murdering a childhood friend over a drug dispute.

He said he tried to turn his life around during the early years of his original 18-year sentence, completing a high-school equivalency degree before enrolling in university classes from prison.

After the riot, LaMar says, prison guards asked him to expose the men responsible in exchange for a reduced sentence, but he refused.

His campaign to have his case reopened has received new support over the past two years.

In addition to his lawyers, he is supported by a group of jazz musicians, led by Brooklyn-based Spanish composer Albert Marques.

Using his prison telephone, LaMar recorded the album "Freedom First" with the jazz group.

LaMar on Thursday welcomed the news, telling AFP it gave him more time to work on fighting "this nightmare."

"As many of you know, three years can come and go in the blink of an eye, so let's take this time to double our efforts, energy and resolve to end this madness once and for all, and for good!" he said in his message.