Two Chinese and two Russian long-range bombers were tracked flying over international waters near Alaska and US and Canadian fighter jets were sent up in response, their joint aerospace command said.

The Chinese and Russian military activity Wednesday was not seen as a threat, the North American Aerospace Defense Command, known as NORAD, said.

“NORAD will continue to monitor competitor activity near North America and meet presence with presence,” the command said in a news release.

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.

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 (370 kilometers) from the shore.

In the latest incident, the Chinese H-6 and Russian Tu-95 aircraft were flying in the North American US Air Defence Identification Zone, an area beyond U.S. and Canadian airspace in which those countries require aircraft to be identified for national security reasons.

The Japanese military has grown increasingly concerned about joint China-Russia drills with ships and warplanes as a potential threat to the security of Japan and the region.

A fleet of Russian and Chinese warplanes including Tu-95s and H-6s were seen flying together last December over the waters between Japan and Korea, the Japanese Defense Ministry said.