Japan has scrambled jets to monitor Russian and Chinese air forces conducting joint patrols around the country, the Japanese defence ministry said late Tuesday, amid rising tensions between Tokyo and Beijing.

Two Russian Tu-95 nuclear-capable strategic bombers flew from the Sea of Japan toward the East China Sea to rendezvous with two Chinese H-6 bombers, and performed a "long-distance joint flight" in the Pacific, the ministry said.

Four Chinese J-16 fighter jets joined the bombers as they made a round-trip flight between Japan's Okinawa and Miyako islands, it added. The Miyako Strait between the two islands is classified as international waters.

Japan also detected simultaneous Russian air force activity in the Sea of Japan, consisting of one early-warning aircraft A-50 and two Su-30 fighters, the ministry said.

Japanese Defence Minister Shinjiro Koizumi said in a post on X on Wednesday that the Russian and Chinese joint operations were "clearly intended as a show of force against our nation, which is a serious concern for our national security."

Japan's fighter jets "strictly implemented air defense identification measures," Koizumi added.

Russian news agencies reported that the Russian-Chinese joint flight near Japan lasted for eight hours, citing Moscow's defence ministry.

South Korea's military also said on Tuesday that seven Russian planes and two Chinese planes had entered its air defence zone.

Japan said on Sunday that Chinese carrier-launched fighter jets aimed radar at Japanese military aircraft a day earlier, an account Beijing disputed.

Beijing's rising military actions near Japan follow Japanese Prime Minister Sanae Takaichi's comment last month that Tokyo could respond to any Chinese military action against Taiwan that also threatened Japan's security.

China and Russia have been ramping up military cooperation in recent years elsewhere, conducting joint operations such as an anti-missile training on Russian territory and live-fire naval exercises in the South China Sea.