Nine Japanese porn actresses pose with three supporters (front) in Tokyo on August 30, 2014, ahead of a "Boob Aid" charity event for AIDS prevention

A group of Japanese porn actresses raised tens of thousands of dollars at the weekend by having their breasts squeezed by fans at a "Boob Aid" charity event for AIDS prevention.

The nine adult movie stars, sporting yellow campaign T-shirts rolled up to reveal their breasts, flashed a big smile as punters approached them at an event that opened Saturday.

Fans sprayed their hands with disinfectant before touching -- quite discreetly in many cases.

A man was seen pressing his palms together in the style of a Buddhist prayer before and after he softly touched the breasts of each of the nine.

Women were occasionally spotted in the mostly male crowd, prompting one of the girls to say in rapture: "Wow, I'm happy. I want her to touch my breasts!"

The event was part of a 24-hour "Stop! AIDS" campaign event in Tokyo, which was also televised live on a Japanese adult cable channel.

The breast-squeezing resumed Sunday morning after an overnight break.

Nearly 6,000 pairs of hands groped for a total of over 15 hours until Sunday evening, organisers said.

About five million yen ($50,000) has been collected, according to the organisers' count one hour before the charity closed. The final sum will be officially announced later.

"I joined Boob Aid for the first time and I didn't know this was an event thousands of people would come to," one of the porn queens, Iku Sakuragi, said after the event.

"I think we should continue this kind of activity," the 21-years-old said, adding she was very happy to see her fans throughout the event.

- 'Squeeze them, donate money' -

The event is the 12th since its launch in 2003. It is backed by the Japan Foundation for AIDS Prevention.

"I'm really looking forward to lots of people fondling my boobs," Rina Serina told the Tokyo Sports newspaper before the event. "But I would be very happy if you would please be delicate."

The bizarre event was staged after sexist heckling of a Tokyo assemblywoman hit the headlines, highlighting old-fashioned views towards women that still permeate Japanese society.

"I never thought my boobs could contribute to society," said the ponytailed Serina, apparently unaware of any contradiction.

Sakuragi had no qualms about being groped by hundreds of pairs of hands.

"It's for charity," she said ahead of the event. "Squeeze them, donate money -- let's be happy."

UN estimates show around 35 million people were living last year with the human immunodeficiency virus (HIV) that can cause AIDS.

Just a fraction of them are in Japan, where a total of 22,971 people were known to be infected with HIV or to have developed AIDS at the end of 2013, according to the National Institute of Infectious Diseases.

But infection has shown no sign of abating with the annual number of new HIV/AIDS patients hitting some 1,500 in recent years, it says.

Japan has one of the developed world's lowest rates of female workforce participation. A lack of childcare facilities, poor career support and deeply entrenched sexism are blamed for keeping women at home.

Prime Minister Shinzo Abe has vowed to create "a society in which women shine" and is expected to bring in more female faces when he reshuffles his cabinet on Wednesday.