Beijing has made serious protests with Tokyo after Japanese Prime Minister Sanae Takaichi deliberately met with personnel from the authorities of China's Taiwan region on the sidelines of APEC meetings and hyped it on social media, urging Japan to take concrete measures to undo the negative impact and stop interfering in China's internal affairs, Foreign Ministry spokesperson said on Saturday.

Takaichi posted on social media on both Friday and Saturday, sharing photos and comments about her meeting and interaction with a personnel that she referred to as "Senior Advisor to the Presidential Office of Taiwan".

The spokesperson said Takaichi's actions seriously violated the one-China principle, the spirit of the four political documents between China and Japan, and the basic norms governing international relations.

Her moves, the spokesperson added, sent a gravely wrong signal to "Taiwan independence" separatist forces and were "egregious in nature and impact".

"The Taiwan question is China's internal affair and at the core of China's core interests. How it is handled bears on the political foundation of China-Japan relations and basic trust in Japan, and is a red line that must not be crossed," the spokesperson stressed.

This year marks the 80th anniversary of the victory in the Chinese People's War of Resistance Against Japanese Aggression (1931-45) and the World Anti-Fascist War, as well as the 80th anniversary of Taiwan's restoration.

Given its long history of colonial rule in Taiwan, Japan bears undeniable historical responsibilities on the Taiwan question and therefore "should all the more act with extra prudence".

"China strongly urges Japan to abide by the spirit of the four political documents between the two countries and honor the commitments Japan has made, reflect on and address its wrongdoings, and take concrete measures to undo the negative impact," the spokesperson said.

The spokesperson also called on Japan to stop interfering in China's internal affairs and to follow through on its commitment to building a constructive and stable China-Japan relationship fit for the new era.