Tokyo on Monday distanced itself from comments by the new head of national broadcaster NHK, who said the Imperial Army's system of wartime sex slavery was not unique to Japan.

Katsuto Momii said Saturday that the practice of forcibly drafting women into military brothels during World War II was "common in any country at war".

"Can we say there were none in Germany or France? It was everywhere in Europe," he told an inaugural press conference, according to local media reports.

His comments came the day before the death in Seoul of Hwang Kum-Ja, aged 90, leaving just 55 South Korean former "comfort women" alive.

The Japanese government on Monday moved to insulate itself from Momii's comments, which it said were a personal opinion.

"Our understanding is that chairman Momii made the comment as an individual", not as the head of Japan's public broadcaster, Chief Cabinet Secretary Yoshihide Suga said.

It declined to comment further on the issue.

Momii, 70, has since apologised for the comments, which he described as a personal opinion.

He conceded they were "extremely inappropriate", and admitted he should not have expressed his personal views publicly, Kyodo News reported Monday.

Momii previously served as a vice chairman of trading house Mitsui, and is rumoured to have been Prime Minister Shinzo Abe's preferred choice as NHK chairman, the news agency said.

During Saturday's press conference Momii had also said the comfort women issue was "complicated because South Korea says Japan was the only country that forcibly recruited (women)".

During Abe's first stint as prime minister in 2007, he provoked region-wide uproar when he said there was no evidence that Japan directly forced women to work as sex slaves.

His administration has struggled to escape the whiff of revisionism, with a recent visit to the controversial Yasukuni Shrine, which counts 14 senior war criminals among the souls it honours, compounding the problem.

"Regarding the comfort women issue, Prime Minister Abe is saddened when he thinks about the people who went thorough sufferings beyond description," Suga said, noting Abe's stance was the same as his predecessors.

"Comfort women" is Japan's preferred euphemism for women drafted into military brothels.

Seoul and Beijing both lashed out at the comments from a man holding an important position, and said they were symptomatic of a larger problem.

"It is deplorable that the head of Japan's public broadcaster, who should remain fair and impartial, has distorted historical facts and made such a ridiculous claim," a South Korean foreign ministry spokesman said.

"The thoughtless remark by the NHK chairman clearly illustrates that historical awareness among leading Japanese figures in Abe's Japan has diminished to a dangerous level."

Chinese foreign ministry spokesman Qin Gang told reporters at a regular briefing Monday that being forced to work as a sex slave caused physical and psychological damage.

"The relevant statement reflects that Japan still has some extremist elements who hope to deny or play down this fact," he said

The issue continues to provoke regional tensions, with South Korea and China insisting that Japan must face up to its World War II-era wrongs.

Historians say up to 200,000 women from Korea, China, the Philippines and elsewhere were forced into brothels catering to the Japanese military in territories occupied by Japan during WWII.

Last year, popular Osaka mayor Toru Hashimoto prompted global outrage last year by suggesting that "comfort women" served a "necessary" role by keeping battle-stressed soldiers in check.

In a landmark 1993 statement, then chief Japanese government spokesman Yohei Kono apologised to former comfort women and acknowledged Japan's role in causing their suffering.