Tension between Japan and China has escalated over the new Japanese leader's suggestion Tokyo could intervene militarily if Beijing attacks Taiwan.

Japan has now warned its citizens in China to be careful of their surroundings and to avoid big crowds amid a diplomatic row over Prime Minister Sanae Takaichi’s comments on Taiwan.

Less than a month into her term, Japan's conservative leader has stirred tensions with China by suggesting a Chinese move against Taiwan could prompt a Japanese military response.

China’s consul general Xue Jian in Osaka was the first to respond, reposting a news article about Ms Takaichi’s comments on social media with the caption, “cut off a dirty neck without a moment of hesitation”, which many understood as a threat to the Japanese prime minister.

From China’s point of view, the Japanese Prime Minister’s remarks on Taiwan test a red line - a trigger that sets this dispute apart from past flare-ups, analysts say.

Japan's Trade Minister Ryosei Akazawa said on Tuesday there are currently no particular changes in China's export control measures on rare earths and other materials. Akazawa's remarks come as Japan seeks to ease tensions with China amid an escalating dispute over Taiwan.