The stigma makes it difficult for those affected to seek treatment

Prejudice against gay people and other at-risk groups was hampering efforts to combat the spread of HIV/Aids, said UNAIDS head Peter Piot.

The UN estimates 8.2m people in Asia have HIV, of whom 5.1m are in India.

The risk of the disease spreading further in the region was now higher than ever, Mr Piot told a conference in the Japanese city of Kobe.

An explosive cocktail of risk factors means that if 'business as usual' continues there will undoubtedly be an explosion of Aids Peter Piot

He said there was a dangerous mixture of insufficient use of condoms, limited access to testing, the widespread use of injected drugs and prostitution.

"An explosive cocktail of risk factors means that if 'business as usual' continues there will undoubtedly be an explosion of Aids," Mr Piot said.

Twelve million extra people could be infected in Asia within the next five years - an increase of 150% - he said.

But, "with major political will", this could be reduced to six million.

Stigma

Homosexuals, drug users and sex workers should be the focus of prevention efforts, UNAIDS says.

But activists say the stigma of HIV makes it difficult for those infected to seek treatment, while prejudice against these groups means not enough money is spent on education programmes to help them protect themselves.

Many people are said to be reluctant to admit their HIV status.

The BBC's Chris Hogg in Tokyo says the problem for Asia is that many people think Aids is not a big issue there.

Around the world, UN figures show about 39m people have HIV/Aids, of whom 25m are in sub-Saharan Africa.