Decrying Japan's recent move over the disputed Senkaku Islands in the East China Sea, China on Monday lodged a protest against a survey conducted by the Tokyo metropolitan government of the islands.
Foreign Ministry spokesperson Hong Lei said in Beijing that Japan's unilateral action was illegal and invalid.
Referring to steps taken by the Japanese government to speed up negotiations on purchasing the privately-owned islands, Hong said efforts by Japan to increase its sovereignty would be of no use.
The Japanese government has reached a general agreement to purchase the islands from their owner for about $26 million.
The government says it negotiated the purchase out of a responsibility to establish Japan's effective control in a peaceful and stable manner.
Documentation on the purchase will be speeded up to complete the islands' nationalization by the end of the current month, according to Japanese media reports.
The islands, known as Senkaku in Japan, Diaoyu in China and Tiaoyutai in Taiwan, are claimed by all the three countries as the region surrounding them is oil-rich and close to key international shipping routes.
The claim over the archipelago, which consists of five islands and three reefs, has long been a cause of friction between Tokyo and Beijing. It is controlled by Japan and forms part of its Okinawa prefecture
Regarding the incident in which a Japanese flag was ripped off the vehicle carrying Japanese envoy in Beijing last Monday, Hong did not reveal details of the on-going investigation. He only said China had already informed Japan of the progress in the investigation.
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