Canadian surveillance planes helping to enforce United Nations sanctions on North Korea are being repeatedly buzzed by Chinese jets that fly so close their crews can see each other, Canada's military has alleged.

In some instances the Chinese warplanes have come so close the Canadian aircraft have had to change course to avoid a collision, the Canadian Armed Forces said Wednesday.

“In these interactions, PLAAF (People's Liberation Army Air Force) aircraft did not adhere to international air safety norms. These interactions are unprofessional and/or put the safety of our RCAF (Royal Canadian Air Force) personnel at risk,” said Dan Le Bouthillier, media relations chief of the Canadian Armed Forces.

A Royal Canadian Air Force CP-140 Aurora arrives at Goose Bay, Newfoundland and Labrador, in 2021.

A Royal Canadian Air Force CP-140 Aurora arrives at Goose Bay, Newfoundland and Labrador, in 2021.

Canada claims the alleged encounters occurred in international airspace during the most recent iteration of Operation NEON, Canada's contribution to enforcing sanctions on North Korea. It did not give specific dates, but said the encounters were increasingly frequent.

The Chinese aircraft sometimes came so close that their air crew was “very clearly visible” to personnel on the Canadian plane, Le Bouthillier said.

The Canadian aircraft involved was a CP-140 Aurora long-range patrol aircraft operating out of Kadena Air Base in Japan. Le Bouthillier said the plane flew out of the Okinawa base from April 26 to May 26.

Canada had taken up the matter with Beijing through diplomatic channels, Le Bouthillier said.

CNN has asked Chinese officials to comment.

Canada's Global News was the first to report the alleged encounters.

The Canadian flights under Operation NEON look for "suspected maritime sanctions evasion activities, in particular ship-to-ship transfers of fuel and other commodities banned by the United Nations Security Council Resolutions,” Le Bouthillier said.

“These sanctions, imposed between 2006 and 2017, aim to pressure North Korea to abandon its weapons of mass destruction programs and respond to North Korean nuclear weapon tests and ballistic missile launches.”

The alleged incidents wouldn't be the first tense encounters between Chinese and Canadian military craft.

In 2019, two Chinese fighter jets buzzed a Canadian warship in the East China Sea in what Chinese media called a “warm welcome.”

The incident between the frigate HMCS Regina and two Chinese Su-30 fighters took place while the ship was in international waters off Shanghai, with the fighter jets coming within 300 meters (1,000 feet) of the Canadian warships bow, according to reports at the time.

There have been other close encounters between Chinese and foreign warplanes over the years.

The worst of these occurred in 2001, when a Chinese fighter jet collided with a US Navy reconnaissance plane over the South China Sea.

In that case, the pilot of the Chinese F-8 fighter was killed and the US plane had to make an emergency landing on China's Hainan Island. The 24 US crew members were held on the Chinese island for 11 days before their release. (CNN)