South Korea expressed regret Thursday over Japan's continued denial of its coercion of Korean women into sex slavery during World War II, sternly warning the country not to gloss over its wartime history.

Seoul's move came in response to Japan's request to the author of a U.N. report condemning Japan's sexual slavery to withdraw part of the content, citing Japanese newspaper Asahi Shimbun's retraction of an article on the issue.

Radhika Coomaraswamy, a former U.N. special rapporteur on violence against women, published the report in 1996 that concluded that Japan's wartime sexual slavery was a violation of international law and urged Tokyo to make an official apology and pay compensation.

Coomaraswamy rejected Tokyo's request, according to Japan's Chief Cabinet Secretary Yoshihide Suga.

South Korea's foreign ministry said that Seoul voiced serious regret over Tokyo's repeated denial of its wartime atrocities related to the issue of sex slaves, the main source of diplomatic tension between Seoul and its neighbor.

"Historical truth cannot be concealed even if Japan tries to gloss over the sex slave issue. Only grave criticism from the international community will follow," said Noh Kwang-il, spokesman for Seoul's foreign ministry. "Seoul will not tolerate Japan's attempt to blur the truth of history."

In June, Japan announced the result of its review of the 1993 landmark statement that acknowledged its wartime sexual enslavement of Asian women for its troops during the war, inviting fierce criticism from Seoul and Beijing. 

The Kono statement, written based on accounts from 16 Korean victims, has been a key element of the basis of relations between Seoul and Tokyo.

But in what Seoul sees as an attempt to backpedal on the official apology, Japan indicated in the review that the statement was the outcome of political compromise between the sides.

Since Japan's Asahi Shimbun in August retracted reports containing late Seiji Yoshida's accounts that Korean women were forcibly dragged into brothels, right-wing Japanese politicians have claimed that the 1993 statement should be revised or nullified.

The Kono statement was not written with Yoshida's accounts while the U.N. report mentioned his accounts as part of evidence supporting the Japanese imperial army's forceful hauling of Korean and other Asian women into brothels.

South Korea demands that Japan show sincerity by settling the issue "effectively and in a way that is agreeable to the living victims," including through an apology and compensation.

Japan has long dismissed Seoul's demands, claiming that all grievances related to its 1910-45 colonial rule of the Korean Peninsula were settled through a 1965 treaty that normalized their bilateral ties.

Historians estimate that up to 200,000 women, mostly from Korea and China, were coerced into sexual servitude for the Japanese army during World War II. Only 54 victims remain alive in South Korea, with their average age standing at 88. (Yonhap)