The tablets were found aboard a ship intercepted by the navy near the town of Kawthoung at the country's southern border with Thailand the previous week.

Police Brigadier General Kyaw Win, of the Home Affairs Ministry's Central Committee for Drug Abuse Control, said the haul was believed to be the largest of the drug in Myanmar, which is a major producer of both heroin and methamphetamine.

"We are surprised that the number of tablets seized is that big," he told AFP, adding that the vessel also contained about 90 tonnes of timber which was thought to be illicit.

He said each tablet was estimated to be worth up to K80,000 (about US$82) on the streets of Yangon -- which would make the total value nearly $200 million -- but that the haul was likely destined for other countries where the price could be different.

"It's important because if it wasn't seized, it will get to Malaysia then to US and other countries. It's expensive and the amount is also high. It's dangerous wherever it reaches," Pol Brig-Gen Kyaw Win said.

He said the largest previous ecstasy seizure was 50,000 tablets in 2005.

Myanmar is the world's second largest opium producer after Afghanistan and is Southeast Asia's biggest synthetic drug maker, says the United Nations Office on Drugs and Crime.

Drug production in the country's war-torn borderlands has surged in recent years, particularly the manufacture of methamphetamine tablets in jungle laboratories.

To mark World Drugs Day in June, Myanmar burnt seized drugs worth about $130 million, including 1.3 tonnes of opium, 225 kilograms (500 pounds) of heroin and 1.2 tonnes of methamphetamine tablets.