China has expressed "grave concern" over Japan's deployment of long-range missiles capable of striking what Tokyo calls "enemy bases".

Japan announced on Tuesday the deployment of the long-range missiles in its Kumamoto and Shizuoka prefectures. Defense Minister Shinjiro Koizumi said Japan "faces the most severe and complex security environment in the postwar era" and must build up its ability to defend itself from outside the region.

In response, Foreign Ministry spokeswoman Mao Ning said on Wednesday that Japan's deployment of offensive weapons under the pretext of "defense" and "counterattack" far exceeds the scope of "self-defense" and "exclusive defense".

This "seriously violates the provisions of documents with binding force of international law, such as the Cairo Declaration, the Potsdam Proclamation and the Japanese Instrument of Surrender, and this seriously violates Japan's Constitution and its existing domestic norms," Mao said.

"This once again shows that Japan's far-right forces are pushing security policies toward offensiveness and expansionism," she added.

The upgraded Type-12 land-to-ship missiles, developed and produced by Japan's Mitsubishi Heavy Industries, became operational at Camp Kengun in Kumamoto prefecture, The Associated Press reported.

The missiles have a range of about 1,000 kilometers, a significant extension from the 200 km range of the original, allowing it to reach China's mainland, according to the AP.

Mao said Japan's "new militarism" is threatening peace and stability in the region. The international community should remain highly vigilant, she said.

"I have also noticed that many Japanese organizations and citizens have clearly expressed their objection," she added.

Last month, a Japanese Self-Defense Forces officer illegally broke into the Chinese embassy in Tokyo with a knife.

"Instead of seriously reflecting on the lack of oversight and control over the Self-Defense Forces, the Japanese side is busy hyping up external threats and accelerating its military buildup. This trend is extremely dangerous," Mao said.

"We solemnly urge the Japanese side to deeply reflect on its history of militarist aggression, live up to its commitments in the field of military security, and act with discretion."