Cambodian Prime Minister Hun Sen on Thursday ordered a probe into an apparent mass HIV infection believed to have been spread by contaminated needles, as the number of suspected cases passed 100.

Hundreds of panicked residents of the remote Roka village in western Battambang province have flocked for testing since news of the infections emerged last week, with health officials saying a total of 106 people may have been infected.

"I call for a thorough investigation into the issue," Hun Sen said in a televised speech, urging tests of the equipment used to verify the patients have contracted HIV.

Teams from the kingdom's Ministry of Health and the World Health Organization (WHO) and UNAIDS have been at the site since Tuesday to review the alarmingly high number of positive results and offer free -- and voluntary -- testing.

"I urge everyone to stay calm and avoid listening to or spreading rumours," Minister of Health Mam Bunheng said in a statement.

"We should also fully respect the privacy of the affected families and ensure they do not face stigma and discrimination."

The outbreak, in the village of around 800 residents, emerged in late November when a 74-year-old Roka man tested positive at a local health centre for the virus, swiftly followed by his grand-daughter and son-in-law, the ministry said.

The spotlight then moved to all of the patients -- including teenagers -- of an unlicensed local doctor, whom villagers suspect of spreading the virus through contaminated needles.

Local media reports said the self-appointed doctor has been questioned by police.

Mean Chhi Vun, director of the Health Ministry's National Center for HIV/AIDS, Dermatology and STDs, said health experts were double-checking the results.

"We need to do more confirmation tests," he told AFP.

Cambodia has been widely hailed for its efforts in tackling HIV/AIDS.

The National AIDS Authority says the rate of HIV infection among people aged 15 to 49 has declined from 0.6 percent in 2013 to 0.4 percent in 2014.

Currently, Cambodia estimates more than 73,000 people live with the disease.

The country is aiming for a zero-percent HIV/AIDS infection rate by 2020.