The Chinese government is protesting Japan’s attempt to name a group of uninhabited islets at the center of a territorial dispute between the two countries.

Japan recently announced plans to name 39 islets near the Diaoyu Islands, which are known as Senkaku in Japanese.

Chinese Foreign Ministry spokesman Liu Weimin said on Monday China has indisputable sovereignty over the Diaoyu Islands, which have been an inherent part of China since ancient times.

He said the Japanese government’s decision to name the islets near the Diaoyu Islands and identify them as Japanese on maps by late March is illegal and invalid.