Police in Laos have made their second huge seizure in three months of methamphetamine, which a UN expert on the illicit drug trade said reflects a breakdown of security in south-east Asia.

Jeremy Douglas, the regional representative for the United Nations Office on Drugs and Crime, said the seizure of 36.5 million methamphetamine tablets in the north-western province of Bokeo was the region’s second largest after 55.6 million more were seized in October in the same province.

He warned that the Mekong River region, where the seizure took place, was experiencing a surge of drug production and trafficking that required strong efforts to bring under control.

“Organised crime treat the Mekong region like a playground — it has all the elements they look for,” he said.

Lao Security Radio, a state broadcaster, said on its website that four residents of the province were arrested on Wednesday in the Huay Xai district in a raid that also captured 590kg (1,300lb) of crystal meth, a minor amount of heroin and a pistol.

Bokeo borders Myanmar and Thailand, a frontier area known as the Golden Triangle which is infamous for the production of illicit drugs.

Heroin and the opium from which it is derived have been joined in recent decades by methamphetamine, mostly produced in Myanmar, especially Shan state.

“Production in Shan is off the charts, and Laos is now a favoured gateway for traffickers,” Mr Douglas said.

Thailand is a major market for drugs from Myanmar, which are also shipped onward to other countries.

Laos is a poor, sparsely inhabited landlocked country with a reputation for corruption that can facilitate smuggling.

Myanmar has been in turmoil since February last year, when the military seized power from the elected government of Aung San Suu Kyi.

It now faces an armed challenge from foes of military rule, disrupting normal law enforcement operations to suppress the drug trade.

The situation is further complicated because drug production is often associated with armed ethnic minority groups involved in political struggles with the government and sometimes with each other.

“Drugs and conflict in Shan have been connected for decades. But as security has broken down, especially the last eight or nine months, we’ve seen an explosion of supply hitting the Mekong and south-east Asia,” Mr Douglas said.

“Neighbours like Thailand and Laos have been flooded with meth in recent months.

“There are no easy fixes given the governance situation in Shan.”

If the region wants to slow drug flows out of the Triangle, Mr Douglas said governments need to get a grip on chemical trafficking, secure borders and make it more difficult to launder money.