UNICEF says Asian cities such as Bangkok, Hanoi and Jakarta have emerged as new transmission hubs for HIV among adolescents.

The Asia-Pacific region is battling a "hidden epidemic" with an estimated 220,000 adolescents between the ages of 10-19 infected with HIV, UNICEF says.

In 2014 alone 50,000 new infections occurred among those aged 15-19, accounting for 15 per cent of all new infections in the region that year, as major cities such as Bangkok, Hanoi and Jakarta have emerged as new transmission hubs, the UN agency reported.

The report warned that adolescents in the most marginalised populations - men having sex with men, transgender people, sex workers, sex trafficking victims and intravenous drug users - are at the highest risk of HIV exposure, even higher than their older peers.

Currently, fewer than one-third of HIV-infected adolescents in the region receive treatment.

Between 2005 and 2014, the AIDS-related death rate rose 110 per cent among adolescents in the Asia-Pacific, while the figure fell by 28 per cent among adults in the same period.