Regional tensions flared on the emotional anniversary of Japan's World War II surrender as activists from China and South Korea used Wednesday's occasion to press rival territorial claims, prompting Japanese authorities to arrest 14 people.

China's official Xinhua News Agency said the arrests of the 14 people, who included Hong Kong residents and mainland Chinese, had caused tensions over its territorial dispute with Japan to surge "to a new high."

Within hours, Chinese Vice Foreign Minister Fu Ying summoned Japan's ambassador to China, Uichiro Niwa, and called her Japanese counterpart, Tsuyoshi Yamaguchi, to protest the detention of Chinese citizens, the Foreign Ministry said.

Fu demanded that Japan release the detainees immediately and without condition, the ministry said in a statement.

The 14 people who were arrested had traveled by boat from Hong Kong to a set of uninhabited islands controlled by Japan but also claimed by China and Taiwan. Japanese police initially arrested five activists who swam ashore in the East China Sea chain, known as Senkaku in Japanese and Diaoyu in Chinese.

Japanese coast guard officers later arrested nine others who stayed on the fishing boat, the Kai Fung 2, including two who had earlier landed on one of the islands and went back on board, officials said. Coast guard officials said the activists were likely to be taken to Naha, the capital of Okinawa prefecture, which has jurisdiction over the islands, for further questioning.

"We want the world to know that this is way back in history the territory of China, and as Chinese people we can go there fishing, touring at our own right," David Ko, a spokesman for the activists, said in a telephone interview from Hong Kong. "The Japanese have no right to stop us."

Chinese activists last landed on the island in 1996, and seven who were arrested were repatriated quickly.

Japan says it has controlled the five main islands for more than 100 years. It has been trying to place four that are privately held under state ownership to bolster its territorial claim.

Chinese patrol vessels have been spotted frequently in the waters, prompting Tokyo to repeatedly protest and beef up its own patrols in the area.

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