DURBAN, South Africa (Reuters) - South African President Thabo Mbeki opened Africa's first international AIDS conference on Sunday and told thousands of health experts that poverty was the continent's biggest killer.

In his address to the 13th International AIDS Conference, Mbeki failed to explicitly say that HIV causes AIDS but he did say his government remained committed to fighting the disease.

Mbeki has courted international controversy by appointing so-called "AIDS dissidents," some of whom doubt that HIV exists or that it causes AIDS, to a presidential panel.

Quoting heavily from a 1995 study by the World Health Organization (WHO), Mbeki concurred that extreme poverty was the world's biggest killer and cause of ill health and suffering.

He told the delegates at the ceremony opening the six-day conference that the South African poverty of which the WHO spoke made AIDS "a partner with poverty, suffering, social disadvantage and inequity":

"As I listened and heard the whole story about our own country, it seemed to me that we could not blame everything on a single virus."

"Let All Voices Be Heard"

Mbeki also used his address to defend his right as South African president to appoint members of his own choosing to the advisory panel, and for all scientists to be heard.

"I believe that we should speak to one another honestly and frankly, with sufficient tolerance to respect everybody's point of view, with sufficient tolerance to allow all voices to be heard...

"Some in our common world consider the questions I and the rest of our government have raised about the HIV-AIDS issue...as akin to grave criminal and genocidal misconduct."

Mbeki's panel has agreed to carry out tests to validate the widely used screening test for HIV, and will report back to the president by the end of this year.

Mbeki said the government remained committed to fighting HIV-AIDS through preventive measures and poverty reduction programs.

Researchers, activists and health officials hope the conference will highlight the AIDS disaster in sub-Saharan Africa, where 24.5 million people are infected.

This goal has been sidelined to some extent by the controversy over Mbeki's interest in the AIDS dissidents.

Continent In Crisis

HIV-AIDS threatens to tear apart the social fabric and economic base of huge swathes of Africa.

"Africa is facing an incredible crisis and that crisis is called the AIDS epidemic. It's an unprecedented crisis that requires unprecedented responses," Peter Piot, the head of the United Nations' AIDS body UNAIDS, told Reuters in an interview.

The Treatment Action Campaign, a South African-based umbrella group backed by 230 AIDS organizations from around the world, marched to demand that pharmaceutical companies make drugs available cheaply to developing nations.

Winnie Madikizela-Mandela, ex-wife of former South African president Nelson Mandela, fired up the crowd of more than 2,000 demonstrators by demanding the South African government fight HIV-AIDS with the same determination that the liberation struggle used to defeat apartheid.

"If we could struggle against HIV with the same commitment as our struggle against apartheid, we can turn back the tide. If we could give the same attention to the struggle against HIV as we did for the bid for the World Cup we could save many lives," Madikizela-Mandela told a crowd of more than 2,000 marchers.