A high-tech Chinese surveillance ship has been tracked off the West Australian coast, close to a secretive naval communications base that supports American and other allied submarines.
Defence Minister Peter Dutton has revealed the auxiliary general intelligence (AGI) vessel was closely monitored by the ADF as it sailed past the Harold E Holt naval station at Exmouth.
Mr Dutton said Australia had been tracking the spy ship in the past "week or so" but didn't put an exact date on the surveillance.
"Its intent, of course, is to collect intelligence right along the coastline," he said.
"It has been in close proximity to military and intelligence installations on the west coast of Australia."
The Defence Minister, who described the situation as unprecedented, said he was concerned not just at how far south the ship had travelled but also that it had "hugged" the coastline as it headed back north towards Darwin.
He dubbed the matter "very strange" and said he expected the ship was collecting as much intelligence as it could.
Shadow Defence Minister Brendan O'Connor said Labor "shares concerns" that the Chinese are conducting surveillance operations off Australia's west coast.
"We note a concerning pattern of behaviour from the PLA Navy of intelligence ships entering Australia economic exclusive zone," Mr O'Connor said in a statement.
Mr O'Connor added that he had a preliminary conversation with Mr Dutton and has sought "a more comprehensive briefing".
Mr Dutton denied that he was making the revelation to stoke national security fears and to woo votes ahead of the May 21 federal election.
Prime Minister Scott Morrison said the ship's proximity to Australia was a reminder of the geo-strategic reality.
"They'll keep a close eye on us and I can assure you, Australia, in our national interest, will always be keeping a close eye on them," Mr Morrison said.
The Prime Minister did not repeat Mr Dutton's claim this was an act of aggression.
"I certainly don't believe that when you take it together with the many coercive acts and the many statements that have been made attacking Australia's nation interest, you could describe it as an act of bridge-building or friendship," Mr Morrison said.
Earlier this year, Prime Minister Scott Morrison accused a Chinese warship of a "reckless and irresponsible act" after a laser was shone at an RAAF aircraft as it approached Australia's northern shoreline.
Home Affairs Minister Karen Andrews has suggested the ship's journey may have been deliberately timed to coincide with the election campaign.
"We all understand that China is very strategic and is very careful about what it does, when it does it, and how it does it."
When asked if he had travelled to Western Australia to make the announcement, Mr Dutton declined to say, citing "operational reasons".
"I think people understand the difficulty, the reality, of the Indo-Pacific at the moment, the acts of aggression from the Chinese leadership and from the Chinese government," he said.
"I think Australians deserve to know what is taking place and it is a repeat of a previous practice where we have made the public aware of these activities before."
The ABC last year revealed the Defence Department had scrapped a contentious proposal to use private security personnel to guard Harold E Holt Naval Communications Station, one of the nation's most secretive and important military facilities.
