Chinese Foreign Minister Wang Yi described the Japanese leader's actions in openly sending signals about Taiwan as shocking and dangerous, thus crossing a red line that Beijing cannot touch.
The statement was the latest episode in a series of tensions that have shaken China-Japan relations for more than two weeks.
According to an official statement from the Chinese Foreign Ministry, Wang accused Japan of trying to interfere in the Taiwan issue, including alleging that Japanese Prime Minister Sanae Takaichi had given the impression that Tokyo was prepared to take military action if China launched an attack on Taiwan.
The statement referred to Takaichi's comments on November 7, in which he stated that any hypothetical attack by China on Taiwan could potentially trigger a military response from Japan.
This situation then triggered the biggest diplomatic crisis between the two countries in recent years.
The tension also spread to the trade and cultural sectors.
On Friday, China took the issue to the United Nations (UN), stating its stance to defend its sovereignty and territorial integrity.
Beijing insists that Taiwan is part of China's territory and does not reject the use of force to reunify the island. In contrast, the Taiwanese government rejects the claim and insists that only the Taiwanese people have the right to determine their future.
Japan's Foreign Ministry dismissed China's claims as unacceptable and stressed that Japan's commitment to regional peace and stability remains unchanged.
Taiwan also condemned China's letter to the UN, describing it as misleading, distorting historical facts and violating the principle of the UN Charter that prohibits the threat or use of force in international relations.
Wang Yi stressed that China will take firm action against any measures deemed to undermine national sovereignty, not only to defend its territory but also to safeguard post-war stability.
He also warned that if Japan persists in what he described as a wrong path, the international community has the right to re-evaluate Japan's military history and reject any revival of a militaristic approach.
In economic terms, China remains Japan's second-largest export market after the United States. In 2024, China will import about $125 billion worth of goods from Japan, mainly industrial equipment, semiconductors and vehicles, according to UN COMTRADE data.
