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Japan on Friday called on South Korea to end its "illegal occupation" of tiny islets and condemned China for its claims over separate islands, saying it would not tolerate recent unauthorized landings by Chinese activists and the South Korean president.

Parliament passed symbolic resolutions condemning South Korean President Lee Myung-bak's visit to the tiny, rocky outcroppings in the Sea of Japan earlier this month and accusing China of allowing activists to land a few days later on a disputed East China Sea island chain.

"Since earlier this month, a series of incidents have occurred, threatening to violate our sovereignty, which we find extremely regrettable. We do not tolerate these actions," Prime Minister Yoshihiko Noda told a news conference.

Noda said that Lee had "illegally landed" on the islands that Japan and South Korea both claim. They are called Takeshima in Japanese and Dokdo in Korean.

"We condemn (Lee's landing) and strongly demand South Korea end its illegal occupation of Takeshima as soon as possible," a resolution passed Friday by lawmakers said. It was the strongest language so far in a dispute that has sent the two countries' relations to the lowest levels in years.

Then last week, a boatful of Chinese activists travelled from Hong Kong to islands in the East China Sea that are controlled by Japan but also claimed by China and Taiwan to push China's claim. All 14 activists were arrested for illegal entry onto one of the islands — known as Senkaku in Japan and Diaoyu in China — released two days later and deported.

Noda, who has come under pressure from critics to take tougher action to protect the islands, announced that Japan would strengthen its patrols in the area around the Senkaku/Diaoyu so further "incursions by foreigners" do not take place. He also said Japan would further push its position that the islands are Japanese territory in international forums.

Chinese Foreign Ministry spokesman Hong Lei reiterated Beijing's claim to the islands. "It is illegal and futile for Japan to strengthen its claim by approving the resolution," he said in a statement. "It does not change the fact that the islands belong to China."

The Chinese activists' landing and a retaliatory one to the same islands last weekend by nationalist Japanese have made the issue one of the biggest territorial flare-ups between the two Asian giants in years, amid persistent animosities over Japan's imperialist past and new fears of China's rising economic and military clout.

Adding to the pressure, Tokyo's nationalist governor Shintaro Ishihara said he wants to visit the Senkaku in October to accompany a coastal and land survey of the islands.

"If I get arrested, that would be fine with me," Ishihara said.

In April, Ishihara announced a plan to use public funds to buy several of the isles from a private Japanese citizen whom Japan says has legal ownership. He acknowledged the move was largely intended to put pressure on Noda's government to play tougher in the islands' administration. Tokyo has since received more than 1 billion yen ($12 million) in donations for the purchase, which is expected to cost between 2 billion and 3 billion yen.

The islands are important mainly because of their location near key sea lanes. They are surrounded in the East China Sea by rich fishing grounds and as-yet untapped underwater natural resources.

Japan annexed them in 1895, saying no other nation exercised a formal claim.

Koichi Nakano, professor of political science at Sophia University, said Japan in some ways is seizing the latest territorial flaps to "publicize Japan's claim, that there is a dispute. To that extent, the Japanese government has been successful. "

Japan's row with China is more complicated than that with South Korea, he said, because the issue has more to do with the relative changes in the international standing of the two countries.

"China is trying to expand its sphere of influence, and that is much more ingrained in the changing geopolitics and therefore unlikely to go away any time soon," he said.

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Associated Press writers Malcolm Foster and Eric Talmadge in Tokyo, and Didi Tang in Beijing contributed to this report.