Russian and Chinese nuclear-capable bombers were intercepted near Alaska on Thursday by US and Canadian fighter jets, their joint aerospace command said.
The military activity, involving Russian Tu-95MS "Bear" and Chinese Xi'an H-6 strategic bombers, flew over the Chukchi and Bering seas and the North Pacific, according to Russia's defence ministry.
"During the flight, Russian and Chinese crews cooperated in the new area of joint operations during all stages of the air patrol," the Russian ministry said.
They added: "At some stages of the route, the air group was accompanied by fighters from foreign countries."
The bomber planes were intercepted by a US F-16 jet and a F-35 fighter jet, as well as Canadian CF-18 fighter jets.
Support aircraft were also involved in the operation, according to CNN.
None of the bomber planes entered US or Canadian sovereign airspace and were “not seen as a threat”, according to the command.
A US defence official said that this marks the first time the two countries have been intercepted during a joint patrol of this nature.
Despite the heightened tensions surrounding the incident, a spokesman for China's defence ministry insisted that the patrols had "nothing to do with the current international situation".
China and Russia confirmed on Thursday that they had conducted a joint air patrol over the Bering Sea, which divides Russia and Alaska.
"Norad will continue to monitor competitor activity near North America and meet presence with presence," the North American Aerospace Defense Command (Norad) command said.
While Russia's military has long been active in the north Pacific, China has emerged as a new actor in recent years as its growing navy and air force expands their presence farther from the country's shores.
The Russian Defence Ministry said the joint patrol also flew over the Chukchi Sea, which is on the north side of the Bering Strait.
Russian fighter jets and strategic bombers were joined by Chinese strategic bombers in the exercises, which lasted more than five hours, the ministry said.
The joint patrol tested and improved co-ordination between the two air forces, said Zhang Xiaogang, a spokesman for China's Defence Ministry.
He said it was the eighth joint strategic air patrol since 2019. He declined to comment when asked if it was the first such patrol over the Bering Sea.
Norad said it had detected the two Chinese H-6 and two Russian Tupolev Tu-95 bombers in the North American US Air Defence Identification Zone, an area beyond US and Canadian air space in which those countries require aircraft to be identified for national security reasons.
A photo released by the Russian Defence Ministry showed a Russian Su-30 fighter jet escorting a Chinese bomber.
Another photo posted online by the military channel of China's state broadcaster CCTV showed Russian and Chinese bombers flying in parallel formation against mostly blue skies.
The Japanese military has become increasingly concerned about joint Chinese-Russian drills and the potential threat to the security of Japan and the region.
A fleet of Russian and Chinese warplanes including Tu-95s and H-6s was seen flying together in December over the waters between Japan and Korea, Japan's Defence Ministry said. At the time, China's Defence Ministry called it the seventh joint strategic air patrol with Russia.
Chinese naval ships have showed up in international waters near Alaska, most recently in mid-July when the Coast Guard spotted four ships in the US Exclusive Economic Zone, which extends 200 nautical miles from the shore.
Mr Zhang described the naval activity as routine combat readiness training and said China would continue to conduct far-seas training to improve the capabilities of its troops.
