Two agents from the United States' Central Intelligence Agency (CIA) fear they were attacked with a sophisticated microwave weapon while visiting Australia late last year, as part of a global campaign by Russia targeting US officials.
The CIA officials reported hearing ringing in their ears and feeling nauseous and dizzy, symptoms consistent with "Havana syndrome", first suffered by American diplomats serving in Cuba.
According to a report in America's GQ magazine, mobile phone data revealed agents from Moscow's Federal Security Service (FSB) were in the vicinity of their hotel room at the time the visitors fell ill.
"While in their hotel rooms in Australia, both of the Americans felt it: the strange sound, the pressure in their heads, the ringing in their ears," GQ reported.
During 2017 the US detailed how mysterious acoustic attacks on employees in its Havana embassy were causing brain-related injuries.
The suspected attack on Australian soil is believed to have occurred at some point during the spring of 2019, before the CIA agents were then similarly targeted when they travelled on to Taiwan.
One of the CIA agents attacked in Australia and Taiwan is understood to be among the agency's five highest-ranking officials.
Department of Home Affairs Secretary Mike Pezzullo told a summit hosted by The Sydney Morning Herald and The Age he had nothing to say about the alleged story.
"I don't have any comment on the story in GQ magazine, and even if I did, I won't confirm or deny if I've had classified briefings on that matter," he said.
"But even if that were the case, I wouldn't be in a position to speak about it."
The US embassy in Canberra referred questions to the CIA, which has not yet responded.
Peter Jennings from the Australian Strategic Policy Institute said if the attacks were proven, Russia was the most likely culprit.
"I think what we are seeing here is something that is most likely from the Russians, who seem to frankly care almost nothing of the consequences of aggressive intelligence actions," he said.
"This is lifting the levels of Cold War-style conflict to new highs.
"If we're actually engaging in things that amount to physical assaults on diplomats and intelligence officials, that's a new thing that we've really not seen before."
Similar attacks have been reported by US officials in countries including Poland, Georgia, the United Kingdom and even in the United States.
