Japanese nationalists landed on an island at the heart of a corrosive territorial row with China on Sunday in a move likely to further inflame tensions with Beijing.

Around a dozen members of the right wing Gambare Nippon (Hang In There Japan) went ashore, an AFP journalist witnessed, saying they intended to plant a Japanese flag at the island's highest point.

The landing comes just days after Tokyo deported pro-Beijing activists who had landed on the island, administered by Japan but claimed by China, which had warned against acts "harming" its territorial sovereignty.

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About 150 people, including eight parliamentarians, arrived at the archipelago in the East China Sea around dawn (8:30 p.m. GMT Saturday) in a flotilla that had sailed from far southwestern Ishigaki.

A Japanese coastguard ship 100 metres from the moored vessels regularly sounded its siren, with loudspeakers telling activists: "Do not moor. Leave the island."

Japan calls the archipelago Senkaku, but it is fiercely claimed by China under the name of Diaoyu.

Local Tokyo politician Eiji Kosaka earlier told an AFP journalist on board one of the boats that participants had to land on the islands, despite an interdiction from the central government.

"We want to give a strong signal to China," he said.

Another participant said activists and politicians wanted to walk onto one of the islands singing Japan's national anthem and would have a meal there.

Some on the boats with fishing rods were trying to catch their breakfast in the fish-rich waters.

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Ahead of the voyage, Kenichi Kojima, a local politician from Kanagawa, near Tokyo, told AFP the trip was about who owned the archipelago, whose waters are believed to harbour rich mineral resources.

"I want to show the international community that these islands are ours. It is Japan's future at stake," he said.

Parliamentarian Keiko Yamatani said most countries recognised Japan's sovereignty over the island chain, but added: "I think this kind of expedition will help raise awareness around the world."

Organizers said ahead of their departure that they would be holding a ceremony aboard boats moored "within touching distance" of the shore, to remember some of those who died in the Second World War.

Beijing on Saturday rebuked Japan over the island visit.

"China has made solemn representations to Japan, demanding that it immediately cease actions harming China's territorial sovereignty," the foreign ministry said in a statement.

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The dispute over the islands is one of the major stumbling blocks -- along with issues related to Japan's military occupation of parts of China during the Second World War -- to smooth relations between Asia's two giant economies.

Tensions spiked as Japan deported 14 pro-China activists who sailed to the islands from Hong Kong.

Some managed to land on an Uotsurijima, the largest island, becoming the first non-Japanese to set foot on any part of the archipelago since 2004.

"China reiterates that any unilateral action taken by Japan regarding" the islands "are illegal and invalid," Saturday's foreign ministry statement said, adding that any such actions would not undermine its claim over the territory.

Separately, a Japanese ruling party heavyweight said Saturday that his country should beef up its coastguard to defend the islands.

"Coastguard officials are doing their best, and so the government and the ruling parties will discuss how to strengthen our backup to them," Seiji Maehara, the policy chief of the Democratic Party of Japan, told reporters.

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The renewed dispute came as tensions also rose between Japan and South Korea after President Lee Myung-Bak visited islets controlled by Seoul but claimed by Tokyo.

Emotions were running high around the August 15 anniversary of Japan's Second World War surrender, with Beijing and Seoul angry about a visit to a Tokyo war shine on Wednesday by two Japanese cabinet members.

China's state-run Xinhua news agency reported Saturday that hundreds of people protested in the western city of Xian over Japan's detention of the pro-China activists.

China's Global Times newspaper welcomed the release of the pro-China activists, but suggested that the dispute with Japan was far from over.

"As long as the Diaoyu Islands are still under Japanese control, there is no complete victory," it said in an editorial.