Australia's defence minister has said a Chinese warship with spying capabilities had been tracked along the nation's western coastline in what amounted to an "aggressive act".
Peter Dutton said the ship was sighted on Friday morning heading north about 250 nautical miles from Broome in Western Australia, and had been hugging the coastline for the past week.
"Its intention, of course, is to collect intelligence right along the coastline," Mr Dutton said.
"It has been in close proximity to military and intelligence installations on the west coast of Australia."
He said it was without precedent for a Chinese warship to venture so far south and that authorities were monitoring the ship closely with planes and surveillance techniques.
He said he wanted to be open and honest with Australians about the situation.
"I think it is an aggressive act, and I think particularly because it has come so far south," Mr Dutton said.
Tensions between China and Australia have been heightened recently after China signed a security pact with the Solomon Islands.
Australians will go to the polls in eight days to vote in a general election. Mr Dutton said the timing of his announcement had nothing to do with the election campaign.
Australia's defence force identified the ship as a Dongdiao Class Auxiliary Intelligence ship named Haiwangxing.
"Australia respects the right of all states to exercise freedom of navigation and overflight in international waters and airspace, just as we expect others to respect our right to do the same," the defence force said in a statement.
"Defence will continue to monitor the ship's operation in our maritime approaches."