SYDNEY: Australian Prime Minister Scott Morrison said an Australian surveillance plane was doing its job when it was "put under threat" with a laser from a Chinese navy ship, rejecting Beijing's assertion the plane came too close.

The P-8A Poseidon - a maritime patrol aircraft - detected a laser emanating from a People's Liberation Army Navy (PLAN) vessel last Thursday, and Australia released photographs of two Chinese vessels sailing close to its north coast.

"Our surveillance planes have every right to be in our exclusive economic zone and keeping a close eye on what people are up to," Morrison told reporters on Tuesday.

"The fact they were put under threat is extremely disappointing," he added.

The Chinese guided missile destroyer and an amphibious transport dock were sailing east through the Arafura Sea between New Guinea and Australia, and later passed through the narrow Torres Strait, Australia's defence department says.

Beijing says the Chinese ships had a legal right to be in international waters, which Australia has not disputed.

China's defence ministry on Monday said the surveillance plane had dropped a sonobuoy, which can help detect submarines, near the Chinese ships, and had flown as close as 4 km (2.5 miles) from the convoy, which it said was "provocative and dangerous". 

Australia's defence department said the aircraft was 7.7 km from the Chinese naval vessel at the time of the lasing incident, and the closest it flew was 3.9 km, which it said was standard for a visual inspection of a vessel.

Morrison said the surveillance plane's crew "were doing their job", and repeated his demand for an explanation from Beijing.

On Tuesday Morrison announced separately Australia would spend A$804 million ($578 million) to buy drones and helicopters and set up mobile stations in Antarctica, because Australia needed to "keep watch" on the region. 

He said that China did not share Australia's objectives in Antarctica, 42% of which is claimed by Australia, and that Beijing wanted to exploit its resources.

"We need to keep eyes in Antarctica because there are others who have different objectives to us, and we need to make sure not just for Australia's interest, but for the world's interest, that we protect this incredible environment that we have responsibility for," he said.


(Reporting by Kirsty Needham. Editing by Gerry Doyle) ((;))