South Korea and China on Thursday told the UN's top human rights forum that Japan must face up to its World War II-era sexual enslavement of women from across occupied Asia, but Tokyo insisted it had already taken responsibility.
"Japan must accept legal responsibility and take appropriate measures," South Korea's ambassador Choi Seokyoung told the UN Human Rights Council.
Chinese counterpart Liu Zhenmin also challenged Tokyo on the issue.
"China urges Japan to apologise for the issue of comfort women and pay compensation," Liu said.
The two ambassadors' remarks were echoed by the Philippines' delegate at the Council, which conducts regular reviews of human rights issues in UN member states.
But Japanese deputy ambassador Takashi Okada took the floor to counter the countries' charges, saying his nation had already sought to make amends.
"The government of Japan feels grieved at the thought of those who suffered such immeasurable pain," Okada said, tapping a term used in a 1993 apology.
"But this should not become a political issue," he added.
He said Japan had been paying into a compensation fund since 1995 and had also paid war reparations to governments. Affected Asian nations insist that Tokyo has not done enough.
Historians say about 200,000 "comfort women" from Korea, China, the Philippines and elsewhere were drafted into Japanese army brothels.
The issue, along with other wartime atrocities perpetrated during the Japanese occupation, has long remained a source of contention between Tokyo and its neighbours, notably South Korea.
In the 1993 statement, Japan offered "sincere apologies" for the "immeasurable pain and suffering" inflicted on comfort women. Two years later, Japan issued a broader apology expressing "deep remorse" for war suffering.
That apology remains passionately opposed by some Japanese conservatives who contend that the country did not directly coerce the women.
Japan's Prime Minister Shinzo Abe -- a conservative who regained power in December 2012 -- has sparked anger amid speculation that he could revise his country's past atonement for the wrongs of World War II.
Abe, whose grandfather was a World War II cabinet minister, is now seen as a pragmatist.
But he was dogged by controversy over history during and after his previous premiership from 2006 to 2007.
His statements on comfort women while in office, and his calls after leaving office for a revision of the apology, sparked an angry reaction elsewhere in Asia.