President Lee Myung-bak strongly criticized Japan for not doing enough to soothe hard feelings Koreans still harbor over its colonial rule, when he made a landmark visit to South Korea's easternmost islets of Dokdo last week, an official said Monday.

Friday's visit to Dokdo, which Tokyo has long claimed as its territory, was the first-ever by a South Korean president. It came days before South Korea observes Liberation Day that marks Korea's independence from Japan's 1910-45 colonial rule, and has sharply raised tensions between the two countries.

"Japan should sincerely apologize as it started a bad war, but it has not done so. That's why pent-up grievances are not resolved," Lee said during the historic visit to the rocky outcroppings in the East Sea, according to a key presidential official.

"Germany has no such problems as it apologized sincerely after World War II."

The harsh colonial rule left deep scars on the hearts of Koreans. During that period, Koreans were banned from using their own language at schools and forced to adopt Japanese names.

Hundreds of thousands of Koreans were mobilized as forced laborers and also as sex slaves, euphemistically called "comfort women."

Unless resolved as early as possible, the sexual slavery issue will remain unresolved forever as elderly comfort women will pass away, Lee said. Only about 60 victims of the sexual slavery are currently alive, and they are well over 80 years old.

"I have no intentions to provoke Japan or create a standoff too much, but Japan has been too insincere about the issues" related to the colonial rule, Lee was quoted as saying during dinner with other people who joined the historic trip to Dokdo.

Lee was also quoted as saying that he wouldn't be able to make the trip if he takes too many things into consideration. A senior presidential aide said the president knew his trip would make noise in Japan, but he appears to have determined that it's time to take action.

Japan has vehemently protested against Lee's trip, calling for Seoul to agree to take the matter to the international court for settlement. South Korea has flatly rebuffed the suggestion, saying it makes no sense to refer what is clearly the country's territory to the court.

Officials said, however, that Seoul has put on hold a series of construction projects aimed at strengthening the country's control of Dokdo, such as building a breakwater or a science research base on the islets as there is concern such projects could damage the environment.

Japan has long laid claims to Dokdo in school textbooks, government reports and other ways, undercutting better ties between the neighboring nations.

South Koreans see those claims as amounting to denying Korea's rights because the country regained independence from colonial rule and reclaimed sovereignty over its territory, including Dokdo and many other islands around the Korean Peninsula.

South Korea has kept a small police detachment on Dokdo since 1954.

(Yonhap News)