The Defence Force has confirmed an Australian special forces soldier has received a threatening letter in the mail, connected to his decision to give evidence to an ongoing Defence inquiry into alleged illegal killings in Afghanistan.
The soldier was cooperating with an ongoing inquiry into the behaviour of Australia’s elite Special Air Services Regiment and the Commandos, headed by NSW judge Paul Brereton.
“Defence confirms that a member of the Special Forces received a threatening letter in the mail, relating to his giving evidence to the IGADF Afghanistan Inquiry,” the Defence spokesperson told SBS News.
“Making such a threat is a criminal offence and Defence has referred the matter to the police.”
The spokesperson said the inquiry did not reveal the identities of witnesses and had conducted its hearings in private.
“Witnesses are protected by law from intimidation and from liability for what they tell the inquiry.”
Defence minister Marise Payne said she was not aware of any similar threats.
"It’s an isolated incident as far as we’re aware, but I don’t intend to comment on it any further," Ms Payne told reporters in Sydney, following the launch of the Invictus Games.
The Chief of the Defence Force, Air Chief Marshall Mark Binskin, said he had "100 percent" trust in the special forces.
The nation's highest-ranking military officer described the threatening letter as a "criminal act".
"I think it is disgusting that a disaffected person thought they could threaten a witness and look to influence the inquiry," Air Chief Marshall Binskin said.
The revelations come as Fairfax Media reports Defence is dealing with a “mafia-style” plot to suppress witnesses to the inquiry.

MP Andrew Hastie has called the action "disgraceful". Source: AAP
Former SASR officer Andrew Hastie, now a Liberal MP who chairs parliament’s Intelligence committee, said the reported threats were “disgraceful”.
Further questions over the culture of special forces soldiers in Afghanistan were sparked this week when a leaked photograph of a Nazi flag flying above an Australian military vehicle surfaced in the media.
Defence said the flag was immediately taken down by a commander.
Prime minister Malcolm Turnbull slammed the behaviour as “completely and utterly unacceptable”.