Prime Minister Scott Morrison -- citing allegations of "serious and possibly criminal misconduct" -- appointed a special investigator, a move to forestall any prosecution at the International Criminal Court.

After the September 11, 2001 terror attacks more than 26,000 Australian uniformed personnel were sent to Afghanistan to fight alongside US and allied forces against the Taliban, Al-Qaeda and other Islamist groups.

Australian combat troops left the country in 2013, but since then a series of often-brutal accounts have emerged about the conduct of Australia's elite special forces units.

They range from reports of troops killing a six-year-old child in a house raid, to a dead foe's hand being severed, to a prisoner being shot dead to save space in a helicopter.

For years the government had tried to suppress whistleblower reports of the alleged wrongdoing, with police even moving to investigate reporters involved in bringing those accounts to the public.

Meanwhile, the Australian Defence Force's Inspector-General conducted one of several closed-door probes into what it called "rumours and allegations" of "possible breaches of the Law of Armed Conflict".

The Inspector-General identified more than 50 incidents, most relating to the unlawful killings of "persons who were non-combatants or were no longer combatants" as well as "cruel treatment".

Morrison said a redacted version of the Inspector-General's report would be released within days, "this will be difficult and hard news for Australians".

The appointment of a prosecutor represents a significant escalation in the legal process and could lead to criminal charges against military personnel.

- 'Brutal truths' -

The military is revered in Australia and its campaigns -- from Gallipoli to Kokoda -- have played a crucial role in fostering the country's identity, as independent of colonial power Britain.

"Serving men and women and our defence forces, both past and present, share the expectations and aspirations of the Australian people for our defence forces, and how they engage in their conduct," said Morrison.

"This is going to be very difficult for Australians" he added. "This requires us to deal with honest and brutal truths, where expectations and standards may not have been met."

There had been speculation that Australia's failure to fully investigate the reports could lead to the International Criminal Court stepping in.

Asked if the appointment of a prosecutor would mitigate that risk, Morrison said: "We believe so, yes. That is the important advice we have taken on this."

"We need to deal with this as Australians according to our own laws, through our own justice processes."

Morrison said an independent panel had also been set up to improve the culture within the armed forces and oversee the defence response to the inquiry.

The matter first came to public attention in 2017 when public broadcaster ABC published the so-called "Afghan files", which alleged Australian troops had killed unarmed men and children in Afghanistan.

In response, Australian police launched an investigation into ABC reporter Daniel Oakes and his producer, Sam Clark, for obtaining classified information -- even raiding the ABC's Sydney headquarters last year, before dropping the case.

Federal police said prosectors "considered a range of public interest factors, including the role of public interest journalism in Australia's democracy" before deciding not to prosecute.