Vietnam's Defence Minister General Phan Van Giang, left, meets with Japan's Defence Minister Nobuo Kishi at the Defence Ministry in Tokyo

Japan and Vietnam on Tuesday signed an agreement to cooperate in space defence and cybersecurity, as the two Asian nations rapidly step up their military ties amid concerns over China's growing assertiveness.

Japan's Defence Minister Nobuo Kishi told reporters that the space and cyberspace agreement aimed to address a "strong sense of urgency" over activities in the Indo-Pacific region that challenge the existing international order, indicating China without identifying any country by name.

Kishi said talks with his Vietnamese counterpart, Phan Van Giang, had taken "defence cooperation between the two countries to a new level."

Tokyo regularly protests the Chinese coast guard's presence near the Japanese-controlled Senkaku islands, which China also claims and calls Diaoyu. Japanese officials say Chinese vessels routinely violate Japanese territorial waters around the islands, sometimes threatening fishing boats.

Kishi also said he raised concerns over the recent escalation of joint military activities by China and Russia near Japanese waters and airspace.

Kishi said a fleet of two Chinese H-6 fighters and two Russian Tu-95 flew from the Sea of Japan to the East China Sea and to the Pacific Ocean, triggering Japanese Self-Defence Force jets to scramble.

Chinese and Russian warplanes previously flew together around Japan twice in 2019, he added.

During the talks, Kishi expressed Japan's strong opposition to "any unilateral attempts to change the status quo by coercion or any activities that escalate tensions," referring to China's increasingly assertive activity in the East and South China Sea.

Japan is committed to protecting a "free and democratic" Indo-Pacific region and cooperating with the United States and other "like-minded countries that share universal values," Kishi said.

Tuesday's deal comes only two months after the two countries struck a deal allowing Japan to provide defence equipment and technology to Vietnam.

Details of the transfer of specific equipment, possibly naval vessels, are still being discussed.

Vietnam is the 11th nation with which Japan has signed a defence equipment and technology transfer deal as Tokyo seeks to support its own struggling defence industry.

Japan is also looking to expand military cooperation beyond its long time ally the U.S., and has signed similar agreements with Britain, Australia, the Philippines and Indonesia.