A Japanese politician has apologised to women forcibly drafted into military brothels during World War II after his comments about them being a military necessity sparked outrage.

On Friday, Osaka mayor Toru Hashimoto issued the apology after two South Korean women in their 80s, who had been used as 'comfort women' in the war, cancelled a meeting with him over fears of becoming political pawns in a long-running row that has stoked tensions between Tokyo and Seoul.

"It is a shame that I couldn't meet them - I wanted to tell them I am sorry for this misunderstanding," Hashimoto told a press conference.

"I hurt them with my words so it's natural that I want to apologise."

Earlier on Friday, supporters of the women said they were concerned Hashimoto would not retract his controversial comments.

"He has to retract his past comments if he wants to apologise and make us believe it is genuine," supporter Pang Chung Ja told a hastily arranged press briefing in Osaka.

She added there were fears the pair could be "politically exploited".

Earlier this month, the mayor said wartime sex slavery served a "necessary" role keeping battle-stressed soldiers in line, setting off a volley of criticism from countries under Japan's rule in the 1930s and 1940s as well as from the US.

The women, who did not appear in public, said in a statement that they were heartbroken by Hashimoto's "outrageous comments" and didn't want to be seen contributing to a less-than-sincere apology.

Instead, they demanded that Hashimoto, 43, apologise and resign as mayor of Japan's second-biggest city.

"We cannot compromise our painful past as victims and the reality that we still live today for Mayor Hashimoto's apology performance,'' the women said in a statement. "We don't need to be trampled on again."

As he apologised for causing hurt, Hashimoto said: "I happen to have used the word 'necessity' but it doesn't mean I personally meant it was necessary ... I mean that it is a historical truth that soldiers were using women. Was it not necessary for them?"