Former commando Kevin Frost reportedly gave a statement to a special inquiry examining allegations of war crimes by Australian troops in the conflict that started with a United States-led invasion in 2001.
The incident allegedly occurred during one of Kevin Frost's three tours of Afghanistan with the Australian Defence Force.
There are no details of the apparent location or date, but the former commando says he was present when another Australian soldier killed a captured enemy fighter.
And he has told the ABC he believes what happened to the prisoner of war amounts to a war crime.
"The particular incident that I was involved in resulted in the POW that I captured actually being executed, murdered. Now, I can't remember if he cut the cuffs off first or if he cut the cuffs off after he shot him. That's one point I can't remember there, because I wasn't looking, I didn't want to look. I turned around, and the guy was dead. He'd been shot through the forehead."
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Kevin Frost says, over the years, his mental health has suffered as a result, as have his relationships with family and friends.
He says he has been treated for depression, counselled and hospitalised for post-traumatic stress disorder.
Now, Sergeant Frost says he is prepared to be investigated, and even prosecuted, for his role in connection with the apparent death of the captured prisoner.
And he says others who were also apparently involved should do the same.
Frost: "I believe I should be punished with the full weight of the law, and justly. I do not believe this should be brushed under the carpet.*
Journalist: "Are you prepared to go to jail?"
Frost: "Yes."
Journalist: "How many incidents do you think there are of breaches of the Geneva Convention war crimes?"
Frost: "I believe there would be many, and I'm hoping what I'm doing now will be a catalyst for these other people to come forward."
Australian troops joined the US-led coalition that invaded Afghanistan in late 2001 in response to the September 11 attacks.
The ABC reports Kevin Frost gave evidence before a special inquiry examining allegations some among Australia's elite forces there may have been involved in war crimes.
New South Wales Supreme Court judge Paul Brereton is reportedly helping the Inspector General of the Australian Defence Force in a broad-ranging review of the claims.
The Defence Department says in a statement the allegations are a subject of an inquiry by the Inspector General of the Defence Force.
Veterans' Affairs Minister Dan Tehan has refused to comment while the investigation is underway.
Justice Minister Michael Keenan, meanwhile, has told the media Australian Federal Police also have the capacity to investigate.
"I am not going to comment on any of the specifics of what you're saying, but, when the police get allegations of criminality, then, obviously, they have procedures that are very well established to be able to follow those allegations and take appropriate action."
The Federal Police say in a statement they have not received any referral in respect to the current Inspector General's inquiry.
