The United Nations has urged all countries with devastating Aids epidemics to launch mass male circumcision programmes following evidence that the surgical procedure can protect against HIV infection.

The World Health Organisation and UNAids, the joint UN programme on HIV/Aids, made the official recommendations after a meeting of experts in Montreux, Switzerland, last month to consider the evidence from three trials in Africa. These had been stopped early when it became clear that the men who had been circumcised were up to 60% less likely to get HIV than those who had not.

Experts accept that circumcision is a sensitive issue as it is tied to social and religious traditions. During sectarian fighting in India, Muslims and Hindus used to distinguish friend from foe by pulling down trousers - all ­Muslims were circumcised.

But research suggests men in Africa would accept male circumcision if it lowered the risk of Aids, and WHO experts held out the prospect of cultural change, al though it might take a decade or more. Catherine Hankins, associate director of the WHO, said that within about 10 years through the 1980s and 1990s, South Korea went from no circumcision of boys to 90% circumcision. It had been influenced by the example of the US.

WHO and UNAids recommend that all heterosexual men should be offered circum-cision in countries with severe Aids epidemics. "We are talking largely or most importantly about countries of sub-Saharan Africa and to a lesser extent eastern Africa," said Kevin de Cock, director of the Aids department at the WHO. But he said it was for countries to decide whether and how to implement the guidance.

He expected that discussions would now take place on the implications in countries in Europe and in the US. However, there is no ­evidence yet that circumcision offers any ­protection to men who have sex with men.

Circumcision could bring many benefits in the long term - it is estimated that universal male circumcision in sub-Saharan Africa, where HIV/Aids is most prevalent, could ­prevent 5.7m new infections and 3m deaths over 20 years.

But the WHO experts have tempered enthusiasm with considerable caution. Circumcision, they say, must not be seen as a magic bullet. It is only partially protective, and they fear some men may assume they can sleep around with impunity and no longer need to practise safe sex techniques, such as wearing a condom.

"We haven't had news like this in an extremely long time," said Dr Hankins. "It is an exciting development, but it is partial protection for men. Circumcised men can still become infected and can still transmit the virus to their partners."

The logistics of actually introducing circumcision are formidable for impoverished countries burdened with Aids and already struggling to test, counsel and treat all who arrive at their clinics. The WHO is recommending that they first focus on adult males, even though the procedure is easier in babies, because it is more urgent to reduce infections in the sexually active age group.

It emphasises the importance of sensitivity, counselling and a lack of coercion when ­offering circumcision and recommends that those who perform it are trained and perform the procedure in a hygienic setting. The WHO also wants donor governments to help fund programmes.

Dr de Cock said the meeting of experts that decided on the guidance proposals disagreed on little, although "there are people who are very concerned that male circumcision has such heavy social and cultural connotations that they would want more data from the world of social science before making any ­recommendations".

Some of them spoke in terms of "symbolism and assault on the body's integrity," he said. But set against that was the enormity of the disaster that Aids represented in Africa. "The thing to me that comes closest to the Aids ­epidemic for its assault on African culture is slavery," said Dr de Cock.