Tokyo's controversial nationalist governor said Tuesday his plan to buy islands at the centre of a festering territorial row with China was akin to locking the doors to keep a burglar out.

Shintaro Ishihara told journalists that Beijing's drive to take control of what Japan knows as the Senkaku Islands and China knows as Diaoyu, was a stage on their journey to get control over the whole Pacific.

"The Chinese have declared that they will take bold steps to break Japan's control (of the islands), including sending more vessels," Ishihara told reporters at the Foreign Correspondents' Club in Tokyo.

"In other words, they are readying to break into someone else's house."

Ishihara, who has made a career out of provocative remarks, many of them aimed at China, last month launched a drive to collect money to buy three of the five uninhabited outcrops from their private Japanese owner.

He accuses the national government of not doing enough to protect them from China, and is apparently riding high on public support for his plan, with about 951 million yen ($12 million) in donations as of Monday.

"An endlessly hegemonic China is now trying to get control of the Pacific, and targeting Senkaku is one of the steps for doing that," a typically ebullient Ishihara said.

"We must lock the doors of the Japanese house more carefully when they have clearly shown their intention to intrude and steal things."

If realised, Ishihara's purchase would mark a new stage in the long-rumbling dispute over the islands, which sit around 2,000 kilometres (1,250 miles) from Tokyo in rich fishing grounds that may harbour lucrative energy resources.

The islands are now owned by the Kurihara family, who bought them decades ago from descendants of the previous Japanese owners.

Ishihara has not revealed the expected cost of the islands, saying only they would not be "too expensive".

The islands were the scene of a particularly nasty confrontation in late 2010 when Japan arrested a Chinese trawlerman who had rammed two of its patrol vessels.

A weeks-long standoff only ended when Japan released the captain in a move widely seen as a diplomatic black eye for Tokyo.