The mayor of Japan's third largest city, Osaka, has apologised for saying that US troops should patronise legal adult entertainment businesses as a way to reduce rapes and other assaults.

Toru Hashimoto, 43, who is also the co-head of an emerging nationalistic party, said on Monday that his remarks two weeks ago rose from a "sense of crisis" about cases of sexual assaults by US military personnel on Japanese civilians in Okinawa, where a large number of US troops are based.

"I understand that my remark could be construed as an insult to the US forces and to the American people'' and was inappropriate, he said at the Foreign Correspondents' Club of Tokyo.

"I retract this remark and express an apology."

Hashimoto had created another uproar when he said that Japan's wartime practice of forcing Asian women, mostly from South Korea and China, to work in frontline brothels was necessary to maintain discipline and provide relaxation for soldiers.

He did not apologise for those comments, but he did call the use of so-called comfort women an "inexcusable act that violated the dignity and human rights of the women, in which large numbers of Korean and Japanese were included".

'Historical truth'

In explaining his ealier statement, 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?"

Hashimoto claimed he had been quoted out of context to say that he personally believed that the use of a "comfort women'' system was necessary.

He was trying to say that armed forces of nations around the world "seem to have needed women'' in past wars and also violated women's human rights during wartime.

Hashimoto said singling out Japan was wrong, as this issue also existed in the armed forces of the US, the UK, France, Germany and the former Soviet Union during the second world war.

"Based on the premise that Japan must remorsefully face its past offenses and must never justify the offenses, I intended to argue that other nations in the world must not attempt to conclude the matter by blaming only Japan and by associating Japan alone with the simple phrase of 'sex slaves' or 'sex slavery'," he said in the statement.

Sexual slavery

Historians say up to 200,000 women, mainly from the Korean Peninsula and China, were forced to provide sex for Japanese soldiers in military brothels.

While some other World War II armies had military brothels, Japan is the only country accused of such widespread, organised sexual slavery.

Hashimoto has become well known in recent years for his outspokenness.

Last year he formed a conservative party, the Japan Restoration Party, with Shintaro Ishihara, a strident nationalist and former Tokyo governor.

The party is now an opposition group in the parliament.

His comments have added to recent anger in neighbouring countries that suffered from Japan's wartime aggression and have complained about the lack of atonement for atrocities committed during that time.