Disgraced American football legend O J Simpson, whose 1995 acquittal for double murder polarised the nation, was granted his release from prison after serving nearly nine years behind bars for armed robbery.

A four-member parole board in the western US state of Nevada voted unanimously to free the 70-year-old Simpson after a tense public hearing broadcast live by news networks.

An emotional Simpson, who bowed his head and mouthed "thank you" to the parole commissioners, could walk free as early as October 1.

"I've done my time, you know?" he told the parole board, which deliberated in private for just 30 minutes before announcing its decision. "I've done it as well and as respectfully as I think anybody can." 

Simpson was found not guilty in 1995 of the grisly murders of his ex-wife, Nicole Brown Simpson, and a male companion, Ron Goldman, in a racially charged case that transfixed America and became known as the "Trial of the Century." 

But the former National Football League running back and actor was sent to prison in 2008 for his role in an armed robbery the previous year of two sports memorabilia dealers at a Las Vegas resort.

Simpson claimed at his trial that he was just seeking to recover personal items from the dealers and he repeated that explanation on Thursday.

"It was my property," he said. "I wasn't there to steal from anybody." 

Simpson initially did not express any remorse for his actions but eventually offered to the parole board that he was "sorry that things turned out the way they did." 

"I had no intent to commit a crime," he said. "If I would have made a better judgment back then, none of this would have never happened." 

Simpson appeared before the parole board by videoconference from Lovelock Correctional Centre, the medium-security prison where he has been serving his sentence.

Seated behind a plain wooden table, he was wearing standard-issue blue jeans, a light blue button-down shirt, a white T-shirt and white sneakers.

Simpson walked stiffly — the legacy of his years on the football field — but appeared to have lost weight and looked healthier than during his last parole board appearance four years ago.

"I've spent nine years making no excuses about anything," Simpson said. "My commitment to change is to be a better person.

"Right now I'm at a point in my life where all I want to do is spend time, as much time as I can, with my children and my friends," he said, before adding jokingly, "believe it or not I do have some real friends." 

Simpson said he intended to settle in Florida upon his release.