BEIJING - China on Monday lodged "solemn representations" with Japan over the island nation's plan to name uninhabited islets of the Diaoyu Islands.

Foreign Ministry spokesman Liu Weimin made the remarks in a press release.

According to media reports, Japan would give names to 39 uninhabited islands, including some surrounding islets of the Diaoyu Islands, and these names would be added to Japan's map by the end of March.

Liu said China has indisputable sovereignty over the Diaoyu Islands and its adjacent islets that have been an inherent part of China since ancient times.

Any unilateral measures taken by Japan on the Diaoyu Islands and its adjacent islets would be unlawful and invalid, said Liu.