Australia will “watch every move” of three Chinese warships which have been detected off the country’s east coast, the defence minister has said.

Three People’s Liberation Army-Navy vessels – the Jiangkai-class frigate Hengyang, the Renhai-class cruiser Zunyiand theFuchi-class replenishment vessel Weishanhu – were detected off north-east Queensland last week and have been surveilled since as they have sailed south. The Financial Times reported the ships were about 150 nautical miles off the coast of Sydney.

The ships’ presence off Australia’s coast closely follows an incident in the South China Sea last week, in which a Chinese fighter jet released flares in front of an Australian military plane.

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The ships have not crossed into Australia’s territorial waters – 12 nautical miles from the coastline – but are inside Australia’s exclusive economic zone (200nm). The ships have not breached international law and the defence force has said its monitoring of the fleet is “routine”.

Australia’s defence minister, Richard Marles, said while the ships’ passage off Australia’s coast was “not unprecedented” it was unusual.

“We are keeping a close watch on them and we will be making sure that we watch every move,” Marles told Sky News.

“And whenever this mission is over on the part of the Chinese task group, we will assess everything we have seen to make a proper assessment of exactly what they were trying to achieve through this mission.”

Australia’s air force and navy were monitoring the ships, he said.

“This is not unprecedented but an unusual event,” Marles said. “Just as they have a right to be in international waters … we have a right to be prudent and to make sure that we are surveilling them, which is what we are doing.”

In a statement on Thursday, the defence department said it “routinely monitors all maritime traffic in Australia’s exclusive economic zone and maritime approaches”.

“Australia respects the rights of all states to exercise freedom of navigation and overflight in international waters and airspace, under international law, particularly the UN convention on the law of the sea.”

The ships’ arrival off Australia’s coast comes as the commander of the US Indo-Pacific Command, Admiral Samuel Paparo, met with Marles and the foreign affairs minister, Penny Wong, in Australia.

Paparo is scheduled to meet Australia’s chief of joint operations in Canberra on Thursday.

A spokesperson for China’s foreign ministry, Guo Jiakun, declined to comment on the ships’ presence in Australia’s EEZ when asked on Wednesday, saying he was “not familiar” with the situation.

According to earlier Chinese media reports, the PLA-Navy frigate, cruiser and replenishment vessel have been conducting “real-combat” exercises in an unspecified part of the Pacific Ocean over the past month.

The three Chinese vessels’ voyage down Australia’s east coast is understood to be the farthest down Australia’s east coast Chinese naval ships have sailed outside an official military visit to Australia.

Chinese ships sailed into Sydney Harbour in 2019 but that visit was undertaken in coordination with the Australian government.

Paparo told the Honolulu Defense Forum earlier this month that China’s escalating military demonstrations of force towards Taiwan were “not exercises; they are rehearsals” for an invasion or blockade of the autonomous island.

Despite the Chinese Communist government never having ruled Taiwan, Beijing claims the island as an inviolable part of its territory and has not ruled out using force to annex it.

Paparo said China had shown “clear intent and capability” to attack Taiwan. Most recently, China conducted a massive simulated air and sea blockade of Taiwan in October as Taipei marked its national day.

In an incident on 11 February, a Chinese PLA-AF J-16 fighter aircraft released flares near an Australian P-8A Poseidon patrol aircraft as it was flying what Australia has said was a “routine maritime surveillance patrol in the South China Sea”.

“This was an unsafe and unprofessional manoeuvre that posed a risk to the aircraft and personnel,” the Australian government said, noting there was no damage to aircraft nor injuries.

China rejected Australia’s protests over the incident, saying the Australian plane “deliberately intruded into China’s airspace” and undermined its national security.

The flare incident was the latest of a number of contested run-ins between military craft from the two countries, following a similar aircraft encounter in the same area last year and a highly controversial report of a Chinese ship deploying sonar in close proximity to Australian navy divers in 2023.

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