A shocking Australian military report into war crimes has found evidence that elite Australian troops unlawfully killed 39 Afghan prisoners, farmers and civilians.

Australian Defense Force Chief Gen. Angus Campbell said Thursday the shameful record included alleged instances in which new patrol members would shoot a prisoner in order to achieve their first kill in a practice known as "blooding." He said the soldiers would then plant weapons and radios to support false claims the prisoners were enemies killed in action.

Campbell told reporters in Canberra the illegal killings began in 2009, with the majority occurring in 2012 and 2013. He said some members of the elite Special Air Service encouraged "a self-centered, warrior culture."

"To the people of Afghanistan, on behalf of the Australian Defense Force, I sincerely and unreservedly apologize for any wrongdoing by Australian soldiers," Campbell said. "Such alleged behavior profoundly disrespected the trust placed in us by the Afghan people who had asked us to their country to help them," Campbell said. "It would have devastated the lives of Afghan families and communities, causing immeasurable pain and suffering. And it would have put in jeopardy our mission and the safety of our Afghan and coalition partners."

As well as the 39 killings, the report outlines two allegations of cruel treatment. It says that none of the alleged crimes were committed during the heat of battle. Only parts of the report have been made public. Many details, including the names of alleged killers, remain redacted.

The report said a total of 25 current or former troops were involved as perpetrators or accessories in 23 separate incidents, with some involved just once and a few multiple times. It said some Australian troops would regularly carry "throw-downs" – things like foreign pistols, radios and grenades that they could plant on those they killed so the Afghan civilians would appear like combatants in photographs.

In March, a video from a soldier's helmet camera, aired on ABC's "Four Corners" showed a Special Air Service (SAS) operator shooting an unarmed Afghan man three times in the head and chest while he cowered on the ground in a wheat field. The incident prompted an investigation into alleged war crimes committed by Australian soldiers in Afghanistan. Fifty-five separate allegations of unlawful conduct in Afghanistan by Australian soldiers were investigated by the Australian Defense Forces (ADF).