Australia's top military officer has savaged the actions of a person who sent a threatening letter to member of the special forces.
The threatening letter related to the soldier giving evidence to an inquiry into the conduct of Australian forces in Afghanistan.
Australian Federal Police have been asked to investigate.
"I think it's absolutely disgusting that a disaffected person thought they could threaten a witness and look to influence the inquiry," Chief of Defence Force Mark Binskin told reporters in Sydney on Friday.
"That's a criminal act and it will be handled appropriately."
Defence Minister Marise Payne was more circumspect.
"Any action of that nature is of course concerning, and I will let the federal police investigation take its course," Senator Payne said.
"It's an isolated incident as far as we're aware, but I don't intend to comment on that any further."