The head of the UN's AIDS prevention agency hailed Nelson Mandela, who on Thursday was fighting for his life in hospital, for his role in breaking the silence and shame surrounding the deadly disease.

"He was the one who really helped us break the conspiracy of silence," Michel Sidibe, the executive director of UNAIDS, told AFP in a telephone interview.

"His legacy is that of non-discrimination, inclusiveness, and making sure that we will continue to fight for the rights of people without rights... That is what he brought to the fight against HIV/AIDS," he added.

Mandela, who spent 27 years behind bars for his struggle under white minority rule and went on to become South Africa's first black president, became a leading AIDS campaigner after completing his single term in office.

In a country where some 5.5 million people, or more than 10 percent of the population, are living with the HIV virus that causes AIDS, Mandela contributed to "giving a voice to the voiceless" suffering from the disease, which claimed his own son in 2005, Sidibe said.

Mandela among other things led the push for HIV sufferers to be given anti-retroviral drugs in South Africa, and launched a campaign for all governments to declare a global AIDS emergency, insisting that fighting the deadly illness was an issue of human rights.

"Fighting discrimination ... and believing in inclusiveness and respecting the dignity of people, that is really what he brought (to the fight against) HIV/AIDS in the 21st century," Sidibe said.

Mandela's successor Thabo Mbeki had drawn international criticism for slowing the roll out of anti-retrovirals and his denial of the link between HIV and AIDS.

Current President Jacob Zuma was similarly pilloried for telling a court hearing that he could not have HIV/AIDS after having sex with a positive partner, because he washed after sex.