"It's clear violence against women is far more widespread in the general population than we thought," said Rachel Jewkes of South Africa's Medical Research Council, who led the two studies. The research was paid for by several United Nations agencies and Australia, Britain, Norway and Sweden. The papers were published online yesterday in the journal .

In the new research, male interviewers surveyed more than 10,000 men in Bangladesh, China, Cambodia, Indonesia, Sri Lanka and Papa New Guinea. The word "rape" was not used in the questions. The respondents were not asked directly whether they had committed rape, but instead were asked questions such as "Have you ever forced a woman who was not your wife or girlfriend at the time to have sex?" or "Have you ever had sex with a woman who was too drugged or drunk to indicate whether she wanted it?"

They were also asked why they had done so.

In most places, scientists concluded between 6 to 8 per cent of men raped a woman who wasn't their partner. When they included wives and girlfriends, the figures were mostly between 30 to 57 per cent.

The lowest rates were in Bangladesh and Indonesia and the highest were in Papua New Guinea. Previous studies of rape have been done in South Africa, where nearly 40 per cent of men are believed to have raped a woman.

Of those men who said they had committed rape, just under half (45 per cent) said they had raped more than one woman.

Prevalence varied widely between locations, though.

The highest prevalence of rape of a non-partner was found among respondents in Bougainville, in Papua New Guinea, with 27 per cent; the lowest was in rural Bangladesh, with 3 per cent.

The investigation is not intended to be an authoritative statistical overview of rape in these six countries or of the Asia-Pacific region, say the authors.

Instead, it seeks insights into where sexual violence may occur and the causes that drive it.

"In view of the high prevalence of rape worldwide, our findings clearly show that prevention strategies need to show increased focus on the structural and social risk factors for rape," Jewkes said.

"We now need to move towards a culture of preventing the perpetration of rape from ever occurring."

Until now, such research has depended mainly on crime reports, which may be sketchy or skewed, or on accounts by women rather than by men.

Taking a new tack, trained male interviewers held lengthy one-on-one encounters with men in cities and the countryside, with the respondents gaining a guarantee of anonymity.

Of those who acknowledged forcing a woman to have sex, more than 70 per cent of men said it was because of "sexual entitlement".

Nearly 60 per cent said they were bored or wanted to have fun, while about 40 per cent said it was because they were angry or wanted to punish the woman.

Only about half of the men said they felt guilty, and 23 per cent had been imprisoned for a rape.

Other findings in the study point to potential causes and risk factors for rape, which in turn helps the search for solutions.

Men who had been sexually abused as a child or raped themselves were likelier to commit rape.

So were those who had a history of physical violence towards a partner, had paid for sex, were members of a gang, had problems with alcohol or had had a large number of sexual partners.

Rape was also more prevalent in places that had been theatres of conflict, such as Bougainville and Jayapura, in Indonesia's restive Papua province.

Asked for an independent comment, Charlotte Watts, a specialist in rape research and a professor at the London School of Hygiene and Tropical Medicine, said the study was bold but thorough and the data was reliable.

"Commonly, much of the debate about violence against women focuses on the need to strengthen laws and provide services for survivors of rape. These are very important," Watts said.

"However, that 30 per cent or more of men in each country who reported having forced a woman to have sex had first done this by the age of 19 speaks to the need to challenge prevalent norms about masculinity and notions of sexual entitlement at an early age."

Tackling alcohol use and childhood exposure to violence were other clear priorities.

The study is one of two analyses from a data mountain called the UN Multi-country Cross-sectional Study on Men and Violence in Asia and the Pacific.

"The problem is shocking but anyplace we have looked, we see partner violence, victimisation and sexual violence," said Michele Decker, an assistant professor at Johns Hopkins Bloomberg School of Public Health, who co-wrote an accompanying commentary. "Rape doesn't just involve someone with a gun to a woman's head," she said. "People tend to think of rape as something someone else would do."