MELBOURNE, Australia (AP) — Australia has protested to Beijing that a Chinese fighter jet endangered an Australian navy helicopter with flares in international waters, officials said Monday.

The incident occurred on Saturday as the Australian air warfare destroyer HMAS Hobart was enforcing United Nations Security Council sanctions against North Korea in international waters in the Yellow Sea, the Defense Department said in a statement.

A Chinese Chengdu J-10 fighter jet released flares in the flight path of an Australian navy Seahawk deployed from the Hobart 300 meters (986 feet) in front of the helicopter and 60 meters (197 feet) above, Defense Minister Richard Marles said.

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“This was an incident which was both unsafe and unprofessional,” Marles told Nine News television.

“We will not be deterred from engaging in lawful activities and activities which are there to enforce U.N. sanctions in respect of North Korea,” Marles added.

There were no injuries or damage, the Defense Department said, adding the Australian government expressed concerns to the Chinese government. There was no immediate comment from Beijing on Monday.

It was the most serious encounter between the two nations’ forces since Australia accused the Chinese destroyer CNS Ningbo of injuring Australian navy divers with sonar pulses in Japanese waters in November last year. Australia said China disregarded a safety warning to keep away from the Australian frigate HMAS Toowoomba.

China maintains that the encounter happened outside Japanese territorial waters and that the Chinese warship caused no harm.

Chinese President Xi Jinping plans to visit Australia this year for the first time in a decade as bilateral relations have improved in recent years from unprecedented lows.