Speakers at the 13th International Aids Conference in South Africa said that more than half of all HIV infections in some groups of men could be prevented by circumcision - the surgical removal of the foreskin.

Recent studies have suggested that being circumcised protects men from contracting HIV and from passing it on to women.

Research has indicated that circumcision helps hygiene by preventing the build up of bacteria behind the foreskin.

Dr Robert Bailey, from the University of Illinois in Chicago, said circumcision could be used as a weapon against HIV and Aids.

"I believe the evidence is now compelling enough to consider adding circumcision to the limited armament we already have against HIV-Aids," he said.

Dr Bailey studied the prevalence of HIV and Aids in the Luo, a group of three million people living in Kenya. He found that men from the group did not practise circumcision and had an unusually high rate of HIV infection.

Another speaker, Dr Anne Buve of the Institute of Tropical Medicine in Antwerp, Belgium, presented the findings of a study into HIV prevalence in four African cities.

She chose two cities with a high level of infection, Kisumu in Kenya and Ndola in Zambia, and two with low rates of infection, Yaounde in Cameroon and Cotonou in Benin.

"In Yaounde and Cotonou, where the HIV prevalence among sexually active adult men was 3.8% and 4.4%, more than 99% of men were circumcised.

I believe the evidence is now compelling enough to consider adding circumcision to the limited armament we already have against HIV-Aids

Robert Bailey, University of Illinois

"Circumcision was less common in Kisumu and Ndola - 26.8% and 7.6% - where the prevalence of HIV was 21.9% and 25.9%."

She supported calls for the introduction of a policy of male circumcision.

But Dr Craig Cohen, from the University of Washington at Seattle, said it was too early to start making health policies promoting circumcision.

This is despite carrying out a study which found a connection between circumcision, sexually transmitted bacterial disease and HIV infection.

He found that bacterial infection of the vagina is more common in women whose partners are not circumcised and that such infection makes a woman more vulnerable to HIV infection.

The studies were presented to the conference on Monday.