WASHINGTON (Reuters) - Male circumcision halves a man's risk of being infected by the virus that causes AIDS in heterosexual intercourse, according to results of two large clinical trials in Kenya and Uganda announced on Wednesday.

Public health leaders hailed the results as pointing to a potentially powerful way to reduce HIV infections in Africa, the continent hardest hit by AIDS.

"It does have the potential to prevent many tens of thousands, many hundreds of thousands and perhaps millions of infections over coming years," Dr. Kevin De Cock, director of the World Health Organization's Department of HIV/AIDS, told reporters.

The U.S. National Institutes of Health (NIH) announced an early end to the two clinical trials after an interim review of the results showed that medically performed circumcisions had a great impact in cutting the HIV infection risk.

A study in Kisumu, Kenya, involving 2,784 men showed a 53 percent reduction of HIV infections in circumcised men compared to uncircumcised men. A parallel study involving 4,996 men in Rakai, Uganda, put the reduction at 48 percent in circumcised men compared to uncircumcised men.

Experts say the prevalence of male circumcision varies greatly from region to region in African countries south of the Sahara, with nearly all men in some areas remaining uncircumcised.Dr. Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases, said the institute agreed to end both trials early and offer circumcision to all men involved in the studies.

The results of the studies seemed to strongly confirm earlier findings about the value of male circumcision in curbing AIDS.

"These results indicate that adult male circumcision could be an important addition to an HIV prevention strategy for men. Male circumcision can lower both an individual's risk of infection and hopefully the rate of HIV spread through the community," Fauci said.

Fauci added that adult male circumcision is not completely protective "and must be seen as a powerful addition to, not a replacement for, other HIV prevention methods."