"Asia has recognized populations of men who have sex with men for quite some time," he said. "The epidemic in these populations started in the mid-1990s. What we see now is a resurgence."

"There are countries where the percentage of people infected are similar to what we were seeing in San Francisco or in Berlin or in London where up to 15 to 20 percent of men who have sex with men are HIV positive," he added.

The report meanwhile noted that unprotected sex between men was a "potentially significant but under-researched aspect of the HIV epidemics in Asia," citing countries such as Thailand and Vietnam.

"Recent study data from several major cities in the region, from Bangkok to Ho Chi Minh City, show increasing HIV prevalence among men who have sex with men," the report said.

In China, unsafe sex between men could account for up to seven percent of HIV infections, it noted.

De Lay said there were also high infection rates among gay populations in cities such as Chennai and Mumbai in India and in Indonesia's capital Jakarta.

He added that these communities often faced homophobia from the wider population, as well as discrimination from health care providers, which discouraged them from seeking information and getting tested.

"Even without blatant national laws that criminalize homosexual behavior, you can still have a gradation of policies and practices that can be almost as bad," he said.