Beijing expressed firm opposition and lodged a strong protest with Tokyo on Friday over the entry of a Japan Self-Defense Forces vessel into the Taiwan Strait, which severely threatens China's sovereignty and security.

The Chinese military has handled the entry in accordance with laws and regulations, Foreign Ministry spokesman Guo Jiakun said at a daily news conference.

Noting that Japanese Prime Minister Sanae Takaichi's erroneous remarks on Taiwan have already inflicted serious damage on bilateral relations, Guo said Japan's dispatch of the Self-Defense Forces vessel into the Taiwan Strait to brandish its military might and engage in deliberate provocation is compounding the wrongdoing.

"It once again exposes the dangerous attempt of certain individuals in Japan to militarily interfere in the Taiwan Strait and undermine cross-Strait peace and stability," Guo said.

He stressed that the Taiwan question bears on China's sovereignty and territorial integrity, as well as the political foundation of China-Japan relations, and constitutes a red line that must not be crossed.

China urges the Japanese side to earnestly reflect on its mistakes, pull back from the brink, exercise prudence in its words and actions, and refrain from going further down the wrong path, Guo said.

The vessel's move marks the latest flashpoint in China-Japan relations, which have deteriorated since Takaichi's erroneous remarks in November.

In late March, a Japanese Self-Defense Force officer intruded into the Chinese embassy carrying a knife, and in the following week, an individual claiming to be a reserve member of the SDF issued an online threat to the embassy claiming a remotely controlled bomb had been planted inside the premises.

When commenting on such harassment and provocation on Friday, Guo noted that these malicious incidents revealed many deep-seated problems in Japan, including the worsening influence of the right-wing, the suppression of objective and rational voices, and the toxicity of the Japanese government's erroneous policies on vital issues concerning China-Japan relations.

He also noted the serious lack of education on true history, the pervasive erroneous historical views, the ongoing push for a more offensive, expansionist and dangerous defense policy, and the failure to supervise the SDF and maintain discipline within the forces.

How to fundamentally address the issue and remove its breeding ground in Japanese society deserves serious pondering by those with insights in Japan, he said.

Attempts to downplay such incidents and even shift attention or blur the line between right and wrong will only lead to more serious consequences, causing greater harm to the Japanese people, he added.