The Philippines has the fastest growing number of HIV infections in Asia, a report by the United Nations and the government showed Tuesday.

The Southeast Asian nation saw a 140 percent increase in new cases from 2010 to 2016, even though the annual number of new infections in Asia-Pacific declined by 13 percent over the same period, according to the report.

"The Philippines has a small window of opportunity to act now and stop a major HIV epidemic from taking hold," Eamonn Murphy, director of UNAIDS Regional Support Team said in a statement.

He called on the government to focus anti-HIV efforts on those at most risk.

Genesis Samonte of the Philippine health department's epidemiology bureau said eight out of 10 reported HIV cases were among men having sex with men (MSM).

"Risky behaviours are starting very young," she said, adding that the MSM group on average started having sex at 16, and anal sex at 17 before they have started using condoms or taken HIV tests, increasing the risk of infection. 

The report also showed that only 35 percent of MSM had comprehensive knowledge of HIV transmission and prevention. 

Samonte said there were indications that a rise in the use of the Internet and cellphones was allowing more young people to have multiple partners, further fuelling the risk of contracting HIV.

Cases will continue to increase and burden the Philippine health system if the nation does not invest in prevention and treatment, according to Samonte. 

Health Secretary Paulyn Ubial said that "HIV is one of the top health priorities for the government,", that the budget for the disease had been sharply increased and her department aimed to start reversing the trend in five years. 

The government was directing its services towards MSM and transgender women, and opening clinics in cities where the bulk of the new HIV cases were detected, Ubial added.