A Chinese intelligence ship tracked off Australia's west coast within 50 nautical miles of a sensitive naval base in the country has given rise to serious concern in Canberra.

Australian authorities kept a close watch on the spy ship over the past week as it sailed past the Harold E Holt naval communications station at Exmouth, in Western Australia, which is used by Australian, U.S. and NATO submarines. 

Prime Minister Scott Morrison said on Friday the Chinese navy vessel was not in Australian territorial waters but its presence was "concerning," according to a Reuters report from Sydney.

China’s aggressive posturing in the Indo-Pacific region and whether it poses a national security threat has been figuring as a major issue in Australia’s election campaign, voting for which will take place on May 21.

Relations between Australia and China have also come under strain due to the increasing Chinese influence in the Solomon Islands as the small Pacific island nation has signed a security pact with China. 

Asked on Saturday about whether the vessel's conduct was a "red line", Morrison said freedom of navigation was permitted around the world and the ship had not broken maritime laws, the Reuters report stated.

"International law of the sea has not been breached," he told reporters on the campaign trail in Melbourne. But he said the issue highlighted challenges Australia faced from China "seeking to impose its will across the region".

The opposition Labour Party leader Anthony Albanese said on Saturday that he shared the government's concerns about the vessel and had sought a briefing.

Defence Minister Peter Dutton said this week that he considered the vessel's movement "an act of aggression" for travelling so far south. 

China's foreign ministry spokesperson Zhao Lijian said he was not aware of specifics but that China always abided by international law and urged Australian politicians to "refrain from alarmism".