Australia's prime minister has joined critics of elite Australian Special Forces troops who were photographed more than a decade ago flying a Nazi flag from a vehicle while on patrol in Afghanistan.

Australian Broadcasting Corp. on Thursday published the photograph of the red flag with a black swastika inside a white circle flying from a Land Rover Long Range Patrol Vehicle somewhere in Afghanistan in 2007.

The secretive culture of the Australia Special Forces, which comprise the Special Air Service Regiment and Commandos, is under a microscope with the Australian Defense Force Inspector General finalizing a two-year investigation into allegations of misconduct. The allegations include illegal killings in Afghanistan.

Prime Minister Malcolm Turnbull described the flag incident as "completely and utterly unacceptable," and said the soldiers involved had been disciplined.