A Chinese naval flotilla set off on Sunday to join Russian naval and air forces in the Sea of Japan in an exercise aimed at "safeguarding the security of strategic waterways", according to China's Defense Ministry.

Codenamed "Northern/Interaction-2023", the drill marks enhanced military cooperation between China and Russia since Moscow's invasion of Ukraine and is taking place as Beijing continues to rebuff U.S. calls to resume military communication.

The Chinese flotilla comprised of five warships and four ship-borne helicopters, left the eastern port of Qingdao and will rendezvous with Russian forces in a "predetermined area", the ministry said on its official WeChat account on Sunday.