A high-tech Chinese spy ship recently detected near the Queensland coast was doing nothing illegal according to the Australian Government, but Beijing's unprecedented military deployment so close to Australia has reignited debate over its activity in the South China Sea.
The Chinese military intelligence vessel was almost certainly monitoring joint military exercises between US and Australian forces.
Its presence, however, could help bolster Australia's case for conducting freedom of navigation operations in the South China Sea.
Why are we worried about this Chinese navy ship off Australia's coast?
It is one of six ships in the Chinese navy set up to intercept communications and signals.
It was loitering in the Coral Sea off Australia's north-east coast while the United States and Australia were involved in huge war games called Exercise Talisman Sabre.
It was inside Australia's exclusive economic zone — but the Defence Department said it did not go inside territorial waters which reach about 22 kilometres from the coast.
The United Nations Law of the Sea says it can be inside Australia's exclusive economic zone (EEZ), but Euan Graham from the Lowy Institute says while it is legal "it is not something ordinary Australians should be expected to welcome".
Is the Government angry?
Foreign Minister Julie Bishop has been quick to point out the ship did not enter Australia's territorial waters. She says other countries are allowed to be inside Australia's exclusive economic zone because that is considered as "international waters".
Defence said the ship's presence had not detracted from the military exercises.
Does Australia do it?
The Defence Force regularly conducts freedom of navigation and freedom of overflight operations in the South China Sea, but unlike the United States, Australian vessels have not come within 12 nautical miles of contested territory claimed by China.
Have other countries done this?
Major military powers regularly conduct maritime surveillance within the EEZ of other nations, and as ANU Professor Don Rothwell argues is "not exceptional".
Recently China has become much more proactive in conducting these surveillance activities, and earlier this month a Chinese ship was spotted off the coast of Alaska reportedly spying on a US ballistic missile test.
What does it mean?
Mr Graham said the Chinese navy's actions could set a precedent Australia's Navy could rely on to fly or sail into China's exclusive economic zone.
