Foreign Ministry spokesman Lin Jian said that an unlawful individual claiming to be an active-duty officer of Japan's Self-Defense Forces scaled the wall and forcibly entered the Chinese embassy in Japan on Tuesday morning.

Speaking at a regular news briefing in Beijing, Lin said the man admitted that his actions were illegal and threatened to kill Chinese diplomatic personnel in the name of so-called God.

"China is deeply shocked by this incident and has lodged solemn representations and a strong protest with the Japanese side," he said.

Lin said that the case, which was "extremely egregious in nature", once again reflected the rampant growth of far-right thinking and forces in Japan, adding that the resurgence of militarism had become a serious danger.

It also exposed the lingering harmful effects of what he described as the Japanese government's erroneous policies on major issues bearing on China-Japan relations, including history and the Taiwan question.

"China demands that Japan immediately carry out a thorough investigation, severely punish those responsible and provide a responsible account to the Chinese side," Lin said.