TOKYO -- Japanese Prime Minister Yoshihiko Nodaon Wednesday denounced South Korean President Lee Myung Bak for his recent remarks, including a demand that Japan's Emperor Akihito apologize for the country's past colonial rule of the Korean Peninsular.

"I don't understand why he made such remarks. It's regrettable, " Noda told local reporters.

The South Korean president's remarks came a day before Liberation Day, when South Korea marked independence from Japan's 1910-45 colonial rule, which was brought to an end with Japan's surrender at the end of World War II.

"If Japan's Emperor wishes to visit South Korea, I think it would be good if he apologizes sincerely to those who passed away while fighting for independence," Lee was quoted as saying on Tuesday.

It was the first time Lee had requested an apology from Emperor Akihito who he invited to visit South Korea during a trip to Japan in April 2008.

The Japanese Emperor has never visited South Korea due to residual ill-feeling over Japan's militaristic past and colonial occupation of the Korean Peninsular.

Japan's Foreign Minister Koichiro Gemba said that Tokyo had officially protested Lee's remarks through proper diplomatic channels and cautioned Seoul that such remarks would only serve to intensify South Korean nationalism, which would not benefit either side.

"I personally think it would not serve South Korea well for Lee to make remarks that could fan nationalism over a difficult problem requiring calm responses," Gemba told local reporters.

Lee's unprecedented remarks followed another first for the South Korean leader who visited a disputed group of islands, known as Takeshima in Japan and Dokdo in South Korea, marking the first time a South Korean president has visited the islets in the Sea of Japan (East Sea).

The ownership of the islands, which are controlled by Seoul but claimed by Tokyo, has been a point of contention between the two nations for decades and the territorial dispute has escalated of late.

Prior to the South Korean president's trip, Tokyo had urged Seoul to cancel the visit, warning its neighbor that any visit would seriously undermine bilateral ties.

Japan's Chief Cabinet Secretary Osamu Fujimura told a news conference that the trip would be completely unacceptable and fly in the face of Japan's position.

Noda told local reporters following Lee's visit and in a sign of protest to South Korea's actions that he had ordered the recall of Japan's ambassador to South Korea.

Gemba indicated to reporters that Japan may seek arbitration of the dispute in the International Court of Justice (ICJ).

Further adding to souring ties between Tokyo and Seoul, a team of swimmers completed on Wednesday morning a 220-kilometer relay, lasting almost 50-hours, with two South Korean students landing on the disputed islets, local media in South Korea reported.

According to the accounts, the event comprising 40 swimmers was to commemorate the anniversary of South Korea's independence from Japan's occupation during 1910-1945, ending with Japan's surrender at the end of World War II 67 years ago.

Visits by two Japanese cabinet ministers to a controversial war shrine in Tokyo on Wednesday also heightened tensions between the two sides, with a South Korean ministry official calling the visits, the first of their kind under the current Democratic Party of Japan leadership, "truly regrettable" and an "irresponsible act. "

Seoul urged Japan to consider the feelings of the countries who had suffered under Japan's past brutal rule and aggression.

"We urge responsible Japanese politicians to face up to history, " the official was quoted as saying.

The Yasukuni Shrine, which honors some 2.5 million Japanese war dead, including 14 major war criminals, is seen as a symbol of Japan's past militarism.

At a ceremony to mark the 67th anniversary of Japan's surrender in World War II, Noda on Wednesday vowed Japan would remain a peaceful nation.

"Japan, as a member of the international society, renews its pledge to ceaselessly seek the realization of international peace, " the Japanese premiere said.

"Japan caused considerable damage and pain to people in many countries, in particular Asian countries. I express deep remorse and offer condolences to the victims and their relatives," Noda said.