(Bloomberg) -- Australian Prime Minister Scott Morrison branded a Chinese navy vessel pointing a laser at one of his nation’s surveillance aircraft off the northern coast an “act of intimidation.”

The incident occurred three days ago when a P-8A Poseidon patrol plane detected a laser from a Chinese naval ship sailing east through the Arafura Sea, Australia’s department of defense said in a statement late Saturday. Morrison responded early Sunday in televised comments in Melbourne.

“I’m very concerned about the actions of using the lasers,” he said. “That is, I can see it no other way than an act of intimidation, one that was unprovoked, unwarranted and Australia will never accept such acts of intimidation.” 

Ties between Australia and China have deteriorated in recent years over issues ranging from investment to alleged foreign interference in domestic politics. They plunged in 2020 when Morrison called for an investigation into the origins of Covid-19, infuriating Beijing. It responded with punitive trade actions targeting Australian commodities from coal to barley, lobsters and wine.

The government in Beijing has increased its control over the South China Sea in the past decade, building artificial structures on disputed territory and sending large ships to prevent neighboring countries from extracting fish and energy from the seas. Australia has responded to the build up by forging closer ties with India and Japan and boosting its own military capabilities. 

The relationship is further complicated by China being Australia’s largest trading partner.

Australia’s defense department said the People’s Liberation Army Navy vessel involved in the laser incident was accompanying another Chinese ship and has since transited through the Torres Strait. Both are now in the Coral Sea, east of Australia, the department said.

Pointing lasers at aircraft can pose a serious risk as they can temporarily blind pilots. The Australian defense department said such actions aren’t in keeping with the standards expected of professional militaries.

“Acts like this have the potential to endanger lives,” it said. “We strongly condemn unprofessional and unsafe military conduct. These actions could have endangered the safety and lives of the Australian Defence Force personnel.”

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