A Royal Australian Navy member deployed on a border patrol operation has died.
The person, who has not yet been named by Defence, was deployed on the patrol boat Cape Inscription as part of Operation Resolute.
In a statement, a Defence spokesman said the cause of death was not yet known.
"On behalf of the men and women of the Australian Defence Force, the Chief of the Defence Force extends his deepest sympathy to the family, friends and shipmates of the deceased member," the statement said.
"Defence is liaising with local authorities and the cause of death is not yet known. As such, it is not appropriate to provide further details at this time."
Defence Minister Marise Payne said the death caused her "great sadness".
"I extend my deepest sympathies and those of the Australian Government to the member's family, colleagues and friends and I express my gratitude for the deceased member's service to our nation," she said in a statement.
Opposition defence spokesman Richard Marles and Opposition spokeswoman for veterans' affairs Amanda Rishworth also issued a joint statement offering condolences and saying the Labor party would request a briefing "at an appropriate time".
"It is a sad day for family, friends and comrades, and we extend to them our deepest sympathies. Our Defence Force members do difficult and extraordinary work to keep our community safe, and we, like the Australian community, value that work deeply," the statement read.
Operation Resolute was launched to stop unauthorised maritime arrivals, piracy, illegal fishing and prohibited imports.
The operation covers close to 10 per cent of the world's surface from the Christmas Island to Norfolk Island.
