An Australian soldier and her husband have been arrested and each charged with spying for Russia.
Investigators say the couple - both Russian-born Australian citizens - obtained Australian Defence Force (ADF) material to share with Moscow, reports BBC.
However, Australian police say "no significant compromise" of military secrets has been identified.
It is the first time stricter foreign interference laws - introduced by Australia in 2018 - have been used to lay espionage charges.
Kira Korolev, a 40-year-old army private, and her 62-year-old husband Igor Korolev faced court in Brisbane on Friday, each on one count of preparing for an espionage offence – which carries a maximum 15-year jail sentence.
Australian Prime Minister Anthony Albanese said he had been "briefed extensively" by the nation's security agencies but would not comment on the case directly as it is now before the courts.
Australian Federal Police (AFP) Commissioner Reece Kershaw said the couple had been in Australia for more than a decade before the alleged offending and had both become citizens several years ago.
Igor worked as a self-employed labourer, and Kira was an information systems technician in the army, a role for which she had obtained a security clearance, police say.
Mr Kershaw alleged she secretly travelled to Russia while on leave from the ADF, then instructed Igor to access her work account and send sensitive material so that she could forward it on to Russian authorities.
An investigation in to whether any of the material was ever delivered to them is still underway, Mr Kershaw said, adding that the charges could be upgraded.
Both Mr Kershaw and Australia's spy agency boss Mike Burgess – who addressed media together on Friday - declined to answer questions about the nature of the documents or how authorities were tipped off about the alleged crimes.
But Mr Burgess said that the ongoing threat of espionage is "real".
"Multiple countries are seeking to steal Australia's secrets. We cannot be naive, and we cannot be complacent."
"If you are spying in this country, we are looking for you. If you are being spied on in this country, we are looking out for you," he added.
Mr Kershaw stressed that Australia's allies could be "confident" that the country would "continue to identify and disrupt espionage and foreign interference activity".
In a statement, the ADF said it was aware one of its members had been arrested and that it "takes all breaches of security seriously".
Bd pratidin English/Lutful Hoque
