Anyone who insists on meddling in China's internal affairs and obstructing China's reunification will inevitably pay a heavy price, a spokesperson of the Chinese Embassy in Japan said on Tuesday.

The Japan Self-Defense Forces and the US military named China as a "hypothetical enemy" for the first time in their joint command post exercise, government sources said on Sunday, Kyodo News reported.

The computer simulation exercise, which began on Feb 1 and is slated to be held through Thursday, envisions an emergency in Taiwan, China, Kyodo News reported.

The embassy spokesperson expressed serious concerns to the Japanese side immediately, clarifying China's firm position. The Japanese side has said that the relevant media report is not true.

For some time, certain forces within Japan have repeatedly stirred up trouble on the Taiwan question, escalating tensions in the Taiwan Strait, inciting confrontation and showing a clear tendency toward recklessness.

Such actions seriously violate the one-China principle and the spirit of the four political documents between China and Japan, the spokesperson said.

"I want to stress that Taiwan is part of China, and the Taiwan issue brooks no external interference. No one should underestimate the Chinese people's strong determination, firm will, and formidable capabilities in safeguarding national sovereignty and territorial integrity," he said.

"If anyone insists on meddling in China's internal affairs and obstructing China's reunification, it will not just be an issue of 'hypothetical enemy', and they will inevitably pay a heavy price," the spokesperson emphasized.