Methadone is a heroin substitute used to treat withdrawal symptoms

Cambodia has launched the country's first methadone-treatment programme, in a new approach to help heroin users.

The World Health Organization (WHO) told the BBC that addiction was widely viewed in Cambodia as a social problem, rather than a health issue.

Until now the government has favoured treatment centres which emphasise hard work and exercise.

But health workers and human rights groups have criticised the facilities, describing them as "labour camps".

The opening of the methadone clinic is the culmination of years of gentle persuasion by organisations which work with drug users.

The methadone programme will be strictly voluntary. Methadone is a heroin substitute used to treat withdrawal symptoms.

Two organisations which run outreach programmes for drug users will identify candidates for treatment.

If they're willing, they will be taken to the clinic for an assessment based on international standards. While the facility is supported by the WHO, it is run by the Ministry of Health inside a public hospital.

But while international health workers are delighted with the new approach, they are still concerned about the existing drug treatment facilities.

The government has no plans to close the centres which it says are voluntary, but which the UN has described as compulsory.

Some residents have complained of being held against their will - and forced to take experimental herbal remedies.