Australia's Defence Minister Peter Dutton has announced a Chinese warship has been tracked "hugging" the West Australian coast.
In a hastily called press conference on Friday afternoon, Mr Dutton said the "warship" in question had "intelligence gathering capability".
He said the ship's purpose would be to collect "as much electronic intelligence" as possible.
Mr Dutton said the ship was sighted on Friday at 6am, lingering about 250 nautical miles northwest of Broome and heading in the direction of Darwin.
The Australian Department of Defence said the ship travelled down to the vicinity of Exmouth in Western Australia, before changing course to "to track east along the north-west coast".
Characterising it as an "aggressive" act, the Defence Minister said it was "very strange" for the vessel to travel so far south.
"It is obviously very strange that it has come this far south and it is hugging the coastline as it goes north, and its intention will be to collect as much electronic intelligence as it can, and, as I say, that is unusual," he said.
The Department of Defence said the People’s Liberation Army-Navy (PLA-N) Intelligence Collection Vessel is named Haiwangxing.
The vessel will be monitored by the department, using air and maritime capabilities.
"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," a statement from the department said.
"Defence will continue to monitor the ship’s operation in our maritime approaches."
Peter Dutton denies announcement was politically motivated
With the Federal Election just a week away, the timing of Mr Dutton's press conference has raised some eyebrows.
When asked if he was making the information public due to the election, Mr Dutton largely avoided directly answering the question.
"We have had vessels in our waters this year and we have made the public aware of those ... we think Australians deserve to know," he said.
He refuted the notion that the press conference was politically motivated but also said Labor "doesn’t take defence seriously".
The two senators vying for the position of the foreign minister have maintained Australia will not blink in the face of a more assertive China.
At a debate on Friday, Foreign Minister Marise Payne and Labor's foreign affairs spokeswoman Penny Wong spoke about Australia's strained relationship with China.
Ms Payne says Australia will continue to seek a constructive relationship with China but would always put its national interest first.
Ms Wong says China could desist from coercive economic measures against Australia to begin repairing the bilateral relationship.
"Our relationship with China has changed because China has changed and we should start from that premise," she said.
"To be very clear, an Albanese Labor government would not take a backwards step when it comes to standing up for Australia's interests."
Do you have a story tip? Email: email@example.com.