A Chinese province that was one of the country's first areas hit by AIDS has banned a group of activists from holding a meeting about how to combat the disease, saying it was illegal, an AIDS group said on Wednesday.

The conference would have brought together 30 Chinese "grass-roots" AIDS activists and experts in the impoverished central province of Henan from Aug. 19-20.

In the 1990s, thousands of farmers in Henan were infected with the disease through schemes in which people sold blood to unsanitary, often state-run, clinics.

Henan authorities scrapped the meeting despite the organisers abiding by demands to prevent foreigners, media or even people from outside the province from participating, Meng Lin from China Alliance of People Living with HIV/AIDS, told Reuters.

"We just wanted to share our experience with other AIDS organisations so as to help patients, and also help the government to fight the disease," Meng, who has AIDS himself, said by telephone.

"The government said our organisation was not registered and was illegal," he added.

A senior Henan government official, who declined to be identified, said he could not comment as he had "no knowledge" of the issue.

China has become increasingly open about tackling a problem once stigmatised as a disease of the decadent West, yet remains wary of the involvement of non-governmental or foreign groups.

Peter Piot, head of the United Nations AIDS agency UNAIDS, said last month during a trip to China that it was essential the government stop harassing or jailing activists.

Earlier in the year, Henan officials tried to stop Gao Yaojie -- a doctor who helped expose the rural AIDS epidemic there -- from going to Washington to collect a human rights award. They let her go after an international outcry.

An estimated 650,000 people are living with HIV/AIDS in China, and health experts say the disease is moving into the general population with most new infections now spread sexually, although drug-users follow closely behind.