China and Russia are set to start joint naval and air drills in the Sea of Japan aimed at safeguarding the security of strategic waterways, as the two countries have pledged to deepen military cooperation.

China’s Defense Ministry said in a statement on its official WeChat account on Sunday that a Chinese naval flotilla, comprised of five warships and four ship-borne helicopters, has set off to participate in the joint exercises, dubbed “Northern/Interaction-2023”.

The vessel left the port city of Qingdao and will join Russian forces in a “predetermined area”, the ministry added.

The English-language Chinese newspaper Global Times, citing military observers, reported that this would be the first time that both Russian naval and air forces will take part in the drill.

Earlier this month, two Russian warships– Gromkiy and Sovershenniy—which are taking part in the Sea of Japan drill, conducted separate training with the Chinese navy in Shanghai on formation movements, communication and sea rescues.

The ships sailed past Taiwan and Japan before making port at the financial hub of Shanghai, prompting both Taipei and Tokyo to monitor the Russian warships.

China and Russia have agreed to expand trade, energy and political relations amid the West’s increasingly adversarial approach over the war in Ukraine.

Washington has become more vigilant about the relations between Beijing and Moscow ever since Chinese President Xi Jinping and Russian President Vladimir Putin struck a “no limits” partnership in February 2022.

China has blamed the United States and NATO for “provoking” Moscow over the Ukraine war and has condemned Western sanctions against Russia.

Russia has also strongly backed China amid the recent tensions between Beijing and Washington over the US political and military interference in Taiwan.