The Australian plane was flying a "routine" surveillance patrol over the contested waters on February 11 when a Chinese fighter jet approached, the defence department said.

The Shenyang J-16 strike jet "released flares in close proximity" to the Australian Poseidon surveillance plane, it said.

"The Australian Government has expressed its concerns to the Chinese Government following an unsafe and unprofessional interaction with a People's Liberation Army Air Force aircraft," the Australian defence department said.

"This was an unsafe and unprofessional manoeuvre that posed a risk to the aircraft and personnel."

Australian Defence Minister Richard Marles said the flares passed within 30 metres (100 feet) of the aircraft, which typically carried around nine people.

No one was injured but Marles said it posed the "potential for significant damage".

He told Sky News that officials had voiced their displeasure with their Chinese counterparts in Canberra and Beijing.

The rebuke coincided with the arrival of three Chinese navy vessels in waters northeast of Australia's mainland.

Defence department officials said a Chinese frigate and a cruiser had been spotted near Australia's "maritime approaches" with a supply tanker in tow.

Marles said it appeared to be unrelated to the aircraft incident but the Australian navy had sent its own frigate to shadow their voyage.

- String of incidents -

"Australia respects the rights of all states to exercise freedom of navigation and overflight in accordance with international law, just as we expect others to respect Australia's right to do the same," the defence department said.

"Defence will continue to monitor the activities of the task group in Australia's maritime approaches with a combination of capabilities, including air and maritime assets."

The mid-air incident is the latest in a string of episodes between China and Australia in the increasingly contested airspace and shipping lanes of Asia.

A Chinese fighter jet was accused of intercepting an Australian Seahawk helicopter in international airspace in 2024, dropping flares across its flight path.

In 2023, a Chinese destroyer was accused of bombarding submerged Australian navy divers with sonar pulses in waters off Japan, causing minor injuries.

The divers had been sailing on an Australian navy frigate, the HMAS Toowoomba, tasked with supporting sanctions enforcement efforts in Japan's exclusive economic zone.

"Australia expects all countries, including China, to operate their militaries in a safe and professional manner," the defence department said on Thursday.

"For decades, the (Australian Defence Force) has undertaken maritime surveillance activities in the region and does so in accordance with international law, exercising the right to freedom of navigation and overflight in international waters and airspace."