Tokyo governor Shintaro Ishihara said Monday that the metropolitan government plans to buy the Diaoyu Islands in the East China Sea, over which both China and Japan claim sovereignty, a move that risks elevating tensions between the two countries.

China reiterated yesterday that the Diaoyu Islands and other affiliated isles have been an inherent part of Chinese territory since ancient times, and China holds indisputable sovereignty over them.

"Any unilateral actions adopted by the Japanese side concerning the Diaoyu Islands and their affiliated isles are illegal and invalid," Chinese foreign ministry spokesman Liu Weimin said.

Ishihara announced the plan of buying three islands in the Diaoyu Islands chain from Japanese private owners during his visit to Washington, saying that Tokyo is going to protect the islands and aims at preventing China from taking "effective control" of the islands.

He said that Tokyo has been negotiating with the owners of the islands and got their approval. A lawyer in charge of the purchase confirmed to the Global Times yesterday that the owners expressed their willingness to sell the islands as long as Tokyo wants to buy them, but that no final decision had been made. 

Ishihara's idea received a mixed response in Japan. The mayor of Osaka regarded the idea as one showing political "wisdom" while the governor of Kanagawa criticized Ishihara's plan, worrying that it would boil over into bigger disputes.

Kyodo News Agency said that the purchase, if realized, would inevitably arouse opposition from China and kindle new conflicts between the two countries.

Liu Jiangyong, a specialist in Sino-Japanese relations at Tsinghua University, told the Global Times that Ishihara's plan was no surprise given his previous provocative words and behavior targeting China. "He is trying to irritate China and purposely damage bilateral relations, which means trouble for the current government but is in his political interests," said Liu.

"His words and ideas do not represent that of the Japanese government and people, so China should not be trapped by his political performance and should continue to solidify bilateral relations," he added. "However, his words might signal the return of right-wing forces in Japan."

Ishihara revealed that he plans to submit the purchase proposal to the metropolitan assembly for discussion in June.

"It is a severe problem. China should negotiate with Japan and warn it. If this proposal is realized, China should strongly oppose it and refuse to acknowledge it," said Su Hao, an expert in international relations at China Foreign Affairs University.

"The Diaoyu Islands have been a sensitive topic between China and Japan and the Japanese government has been prudent in this. Ishihara obviously wants to cause trouble here," he said.  

Agencies contributed to this story