Blair said at a news conference that a Chinese fighter jet on Oct 29 twice flew close to a Canadian Cyclone helicopter near the Paracel Islands, in the South China Sea, and on the second flyby fired flares “directly in front” of the helicopter.

There was “little separation” between the fighter jet and the helicopter, he said.

“The actions of the People’s Republic of China fighter jet were deemed to be significantly unsafe, and we’ll express our concerns to the People’s Republic of China about that.”

The helicopter and HMCS Ottawa were in the South China Sea as part of US and allied “freedom of navigation” crossings to reinforce the status of the body as an international waterway.

Beijing claims almost the entire South China Sea, through which trillions of dollars in trade passes annually, and has ignored an international court ruling that its assertion has no legal basis.

China’s assertiveness in the South China Sea via the deployment of hundreds of vessels and aircraft to the area, which has led to recent clashes with Philippine and Vietnamese ships, has become a growing concern for Washington and its regional allies.

Washington recently accused Beijing of orchestrating a “concerted” campaign of dangerous and provocative air force maneuvers against US military planes flying in international airspace in the region, warning such moves could spark inadvertent conflict between the two powers.

In mid-October, Chinese fighter jets also buzzed a Canadian Aurora maritime patrol aircraft helping to enforce United Nations Security Council sanctions against North Korea in response to its nuclear weapons tests and ballistic missile launches.

Blair had called the latter actions by the Chinese air force – coming within 5m of the Canadian plane – “dangerous and reckless.”

Beijing hit back, accusing the Aurora plane of having “illegally intruded into the airspace” of Chiwei island, which lies in the Japan-administered Senkaku Islands, claimed by China.