Japan’s leader says that his government is negotiating to buy islands in the East China Sea that are at the centre of a territorial dispute with China, a move that could elevate tensions between the Asian powerhouses.

Prime Minister Yoshihiko Noda told reporters Saturday that he’s considering nationalising part of the islands to strengthen Japan’s control over them amid China’s increasing territorial claims in the region.

Surrounded by rich fishing grounds, the uninhabited islands called Senkaku in Japanese and Diaoyu in Chinese are claimed by China, Japan and Taiwan and are a frequent flash point in diplomatic relations.

Mr. Noda said Japan effectively controls the islands that are “undisputedly part of Japan’s inherent territory by historical evidence and international law.” But he acknowledged trying to purchase the islands from a private Japanese citizen, whom Japan says has legal ownership, as an option to strengthen their defence.

“We are talking to the owner as we make a comprehensive study of how we can maintain control over the islands peacefully and stably,” Noda told reporters during his visit to the disaster-hit northern Japan.

In China, Foreign Ministry spokesman Liu Weimin reiterated Beijing’s position that the islands are Chinese territory. “China’s holy territory simply cannot be allowed to be bought or sold by any person,” Liu said in a statement.

Liu said the Chinese government would continue to take necessary measures to “resolutely safeguard the sovereign rights of the Diaoyu Islands and adjacent islets,” according to the statement posted on the ministry’s website.

Japan says it leased out the five main islands for free over 100 years ago, and that four of them have since been sold to private owners, with the fifth remaining state property. The government pays rent on the four privately—owned islands to keep them from being sold to any questionable buyer. It pays 24.5 million yen ($304,000) a year to a private Japanese citizen whom Japan says has legal ownership for three islands, which are unused, according to the parliamentary records. The fourth island, whose rent is not disclosed, is used by the U.S. military for drills.

Tokyo Gov. Shintaro Ishihara revealed in April that he was in purchase talks with the owner of the three islands, saying his move was largely intended to put pressure on the government to play a bigger role in the islands’ administration. He said he plans to use public funds to buy several islands.

Tokyo has already received more than 1.3 billion yen ($16.3 million) in donations for the purchase, which is expected to cost between 2 and 3 billion yen.

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