China expresses grave concern over Japan's move to deepen cooperation with NATO, Chinese Foreign Ministry spokesperson Lin Jian said on Monday.

Lin made the remarks when asked to comment on Japan's announcement that it would dispatch four Self-Defense Forces personnel to the NATO Security Assistance and Training for Ukraine headquarters in Germany for the first time.

Japan has been pursuing remilitarization at full throttle, engaging in frequent interactions with a military organization from outside the region, expanding the scope of activities of its Self-Defence Forces and building a combat-ready operational system, Lin said at a regular news briefing.

"This is Japan trying to break free from the constraints of its Constitution, domestic and international laws, and its 'exclusively defense-oriented' principle, challenging the postwar international order," Lin said, adding that Japan portrays itself as a "peace-loving country," but its actions are in the very opposite direction.

Noting the malevolent emergence of neo-militarism in Japan is putting regional peace and stability under threat, he called on the international community to stay on high alert and take resolute countermeasures.