Chris Beyrer, president-elect of the International Aids Society (IAS), issued the warning in Friday's closing speech to the conference in Melbourne, Australia.

"A wave of discriminatory laws and policies are setting us back towards exclusion: limiting rights, reducing health care access and aiding and abetting the virus," Beyrer said.

Beyrer pointed to anti-gay laws introduced in a number of countries, including Russia, Nigeria and Uganda, or one banning sodomy that has been reintroduced in India.

A recent United Nations report said that a total of 79 countries had laws on the books that criminalize same-sex practices.

Aids activists argue that HIV spreads more easily when certain groups in society, such as sex workers, gays or intravenous drug users, are criminalized. This is partly because it makes it more difficult to educate people about safe sex practices.

Stigma and discrimination

South African Human Sciences Research Council CEO Olive Shisana told the conference that stigma and discrimination stemming from such legislation continued to "hinder the implementation of science on the ground."

United Nations data shows that 35 million people are currently living with the Human Immunodeficiency Virus (HIV), which causes AIDS. It also shows that while the vast majority of cases are in sub-Saharan Africa, it is on the rise in both Russia and Ukraine, particularly among intravenous drug users, prisoners, and sex workers.

Organizers said around 20,000 people, more than 13,000 of them delegates, had attended the Melbourne conference over the past six days. The opening of the conference had been overshadowed by the crash of Malaysia Airlines flight MH17 in easten Ukraine, in which six delegates to the conference, including leading Dutch researcher Joep Lange, a former president of the International AIDS Society, died.

The next International Aids Conference is to be held in the South African port of Durban in 2016.

pfd/tj (dpa, AFP)