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.

Chief Cabinet Secretary Osamu Fujimura said that Japan historically and by international law owns the islands, and that there is no room for its sovereignty to be questioned. He called the trespassing "extremely regrettable."

The handling of the arrested activists is extremely sensitive. Japan has the option of repatriating them or sending them to criminal court.

Japan's arrest and weekslong detention of a Chinese fishing boat captain in 2010 after his vessel collided with Japanese patrol boats near the disputed islands triggered the worst diplomatic dispute in years between the two countries, prompting Beijing to suspend some exports and cancel high-level talks.

Also Wednesday, a group of South Koreans reached another set of disputed islands controlled by South Korea in a demonstration aimed at belittling Japan's claims to that territory.

The anniversary of Japan's surrender in 1945 revives long-running territorial disputes in Asia as well as emotional memories of Japan's brutal colonial occupation of many neighbors that ended only at the close of the war. While Japan routinely apologizes for its wartime actions, its politicians often anger neighboring countries by visiting the Yasukuni Shrine, a memorial to Japan's war dead, including top war criminals.

Dozens of Japanese lawmakers visited the shrine Wednesday, including two Cabinet ministers.

At a solemn ceremony elsewhere in Tokyo, Prime Minister Yoshihiko Noda apologized to victims of Japanese atrocities, mourned the dead and renewed Japan's pledge to renounce war.

"We have caused tremendous damage and pain to many countries, particularly the Asian people, during the war. We deeply regret that and sincerely mourn for those who were sacrificed and their relatives," Noda said. "We will not repeat the same mistake."

Emperor Akihito, whose father made the unprecedented 1945 national radio address announcing that the war could not be won, also offered prayers for the dead.

Simmering tensions between Japan and its neighbors have threatened to boil over in recent weeks.

Last week, South Korean President Lee Myung-bak visited contested islands in the Sea of Japan called Takeshima in Japanese and Dokdo in Korean. His visit was seen by many as an attempt to play up anti-Japan sentiment ahead of elections later this year.

Japan lodged a protest to South Korea over Lee's comment Tuesday that Akihito should apologize to Koreans if he wants to visit the country, saying Tokyo has never discussed or pushed for an Imperial visit. Foreign Minister Koichiro Gemba also said Japan was considering taking the island dispute to an international court.

A group of South Korean protesters, swimming across the sea in a relay, reached the island on Wednesday.

In a ceremony Wednesday celebrating Japan's defeat, Lee condemned Japan for forcing thousands of Korean women into sexual slavery for Japanese soldiers during the war.

Historians say up to 200,000 women from Korea, China and the Philippines were forced to provide sex to Japanese soldiers at military brothels during the war. Japan has apologized and initiated a private fund as a way to pay the women without providing official compensation, but many of the women rejected the offer, demanding a formal apology and state compensation.


Associated Press writers Kelvin Chan in Hong Kong, Didi Tang in Beijing, Annie Huang in Taipei, Taiwan, and Sam Kim in Seoul, South Korea, contributed to this report.