YANGON/BANGKOK - Myanmar, Thailand and Cambodia torched nearly $1 billion worth of seized narcotics on Monday, a defiant show of force as police struggle to stem the rising flow of drugs in the region.

The burnings, to mark the United Nations' world anti-drugs day, follow another year of record seizures of narcotics from the remote borderlands of Myanmar, Laos, southern China and northern Thailand.

Myanmar is one of the world's largest drug-producing nations, a dark legacy of decades of civil war.

Armed gangs churn out vast quantities of opium, heroin and cannabis and millions of caffeine-laced methamphetamine pills known as yaba which are then smuggled out across Southeast Asia.

Drugs worth of estimated $385 million were burned in three official ceremonies around Myanmar on Monday, according to a senior police officer in the capital Naypyidaw.

At the biggest bonfire in Yangon, huge clouds of smoke filled the sky as authorities set fire to stacks of opium, heroin, cocaine and methamphetamine tablets worth almost $230 million.

"We burned a record amount of drugs today ... because police have seized more in recent years," said Myo Kyi, a local drug enforcement officer.

On an industrial estate on the outskirts of Bangkok, Thai authorities incinerated some $590 million worth of drugs including 7,800 kilograms of yaba pills and 1,185 kg of the more potent crystal methamphetamine.

And in Cambodia, officials burned 130 kg of drugs estimated to be worth some $4 million.

The huge seizures are often touted as proof these countries are making inroads into the vast regional drug trade.

Myanmar has been struggling to stem a growing tide of drug addiction inside its borders.

Experts said yaba use has exploded as ethnic armed gangs switched from exporting all the pills abroad to increasingly targeting domestic users.

"Drug production has increased every year since 2006," Yangon police chief Win Naing told crowds gathered for Monday's ceremony on the outskirts of the city.

In a bid to combat the growing scourge, Myanmar's new government is seeking to overhaul stringent anti-drug laws brought in under the former government.

Current legislation means anyone found with even small amounts of drugs can be jailed for years.

Thailand, meanwhile, has the world's sixth-largest prison population and the tenth highest incarceration rate in the world, largely thanks to its strict anti-drug laws.

The market for methamphetamines has been growing in Southeast Asia, the UN has said. It estimates that Southeast Asia's trade in heroin and methamphetamine was worth $31 billion in 2013.

Afp - Reuters