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TOKYO (AP) — Japan apologized Tuesday to South Korea for its colonial rule over the country, seeking to strengthen ties between the two countries ahead of the 100th anniversary of the Japanese annexation of the Korean peninsula.

During Japan's occupation from 1910-45, many Koreans were forced to fight as front-line soldiers, work in slave-labor conditions or serve as prostitutes in brothels operated by the military. Older Koreans still remember atrocities committed by Japan, and the issue remains sensitive decades later.

"For the enormous damage and suffering caused by this colonization, I would like to express once again our deep remorse and sincerely apologize," Prime Minister Naoto Kan said in a statement approved by the Cabinet.

The statement apologized specifically to South Korea, in contrast to earlier apologies by Japan for wartime actions made broadly to the country's Asian neighbors. Japan has no diplomatic relations with communist North Korea, which had no immediate response to Kan's apology.

Seoul accepted the apology, although President Lee Myung-bak does not plan an official response, said presidential spokesman Cho Hyun-jin.

"We hope that through proper recognition and reflection of the unfortunate history, close bilateral relations can further develop into a partnership for the future," said South Korean Foreign Ministry spokesman Kim Young-sun in a statement.

The Japanese leader also said his country would soon return some Korean cultural artifacts, including historical documents, that it acquired while ruling the region. Kan later spoke to Lee on the phone, and the two leaders agreed to continue to work to stabilize Asia.

Some victims of Japan's rule called Tokyo's apology insufficient, saying it should be backed up by specific measures such as reparations for victims, prosecution of wrongdoers and a record of the Japanese military's history of sexual slavery in Japanese textbooks.

Later Tuesday, about 50 South Korean activists rallied in front of the Japanese Embassy in Seoul, urging Tokyo to offer a more sincere apology and return all Korean cultural artifacts in its possession.

"We no longer welcome apologies of words without action," lead activist Yang Soon-im said.

The apology comes ahead of the 100-year anniversary of Tokyo's annexation of the Korean peninsula on Aug. 29.

Despite their troubled history, Tokyo and Seoul remain closely tied economically and militarily. Both countries host tens of thousands of U.S. troops, and Japan was quick to stand by South Korea after it accused North Korea of sinking one of its warships in March, killing 46 sailors.

"The Asian economy is expanding very rapidly. Through the cooperation of Japan and Korea, plus the U.S., the increased stability of the region can be achieved by these three nations, and this is very meaningful," Kan told reporters after the apology had been issued.

Japan's occupation of Korea ended when it surrendered to the U.S. in 1945 at the end of World War II. The peninsula was later divided into separately-governed regions resulting in a communist North and capitalist South.

Tokyo has a long history of discord with North Korea, which has admitted kidnapping its citizens in the past and conducted long-range rocket tests over its main island.

Japanese leaders have repeatedly apologized in the past for aggression against its Asian neighbors. An apology in 1995 marking the 50th anniversary of the end of World War II has become the government's official stance.

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Associated Press writers Sangwon Yoon and Hyung-jin Kim in Seoul contributed to this report.