A high-tech Chinese spy ship has been spotted off the Queensland coast monitoring joint military exercises between Australia and the United States, in what Defence officials have described as an "unfriendly" and "provocative" act.

The ABC can reveal the Auxiliary General Intelligence (AGI) vessel from the People's Liberation Army was sighted by the Defence Force in international waters during this month's Talisman Sabre war games.

The Type 815 Dongdiao-class AGI vessel is fitted with advanced communications systems designed to eavesdrop on other militaries.

In a statement to the ABC, Defence confirmed the spy ship had "been operating off the north-east coast of Australia" during the joint military exercises.

"The Chinese vessel has remained outside Australian territorial waters but inside the Australian Exclusive Economic Zone in the Coral Sea," the department said.

"Exercise Talisman Sabre is currently taking place in the vicinity. The vessel's presence has not detracted from the exercise objectives," it added.

A US helicopter picks up troops during Talisman Sabre.

Euan Graham from the Lowy Institute said the deployment of the vessel was an alarming development.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 2 minutes 41 seconds 2 m 41 s Listen to the story Download 4.9 MB

"I'm personally not aware of any publicised appearance of an AGI off the Australian coast before," he said.

"Coinciding with the joint exercise with the United States — clearly that sends quite an unfriendly message."

Senior Australian military figures also told the ABC China's actions were provocative and sent an unfriendly message.

"At the moment what we see is a double standard where China picks the areas of the Law of the Sea that it likes and refuses to implement those that it doesn't," Dr Graham argued.

"I think it can only expect that to come back as a message in force from Australia and other countries."

The Defence Department said Australia respects the rights of all states to exercise freedom of navigation in international waters in accordance with international law.

Just days ago the Defence Force hosted a senior Chinese PLA General in Australia on a so-called "goodwill" visit.

During the trip, General Wei Liang "exchanged views on regional security issues" including the territorial dispute in the South China Sea.