YANGON -- Myanmar arrested 420 drug traffickers last month, state media reported Saturday, as the world's second-largest opium producer sought to show it was cracking down on the narcotics trade.

The UN anti-drugs body has said opium production in Myanmar shot up 46 percent from 2006 to 2007, but the military-ruled nation continues to insist that it is on track to be drugs-free by 2014.

"Action was taken against 420 persons -- 346 men and 74 women -- in 265 cases in August 2008," the junta-run New Light of Myanmar newspaper said.

Police, customs and military also seized some 151 kilograms (333 pounds) of opium, 7.5 kilograms (16.5 pounds) of heroin, 1,263 kilograms (2,784 pounds) of low-grade opium and 142,955.5 stimulant tablets, along with other batches of narcotics and chemicals, the paper said.

Myanmar's mountainous and lawless border regions once hid vast poppy fields which supplied most of the world's opium well into the 1990s.

Under pressure from governments including close ally China, Myanmar eventually began a campaign in the 1990s to eradicate the crop, and soon Afghanistan took its mantle as the world's top opium producer.

But after a few years of steep decline, opium production in Myanmar has risen once again.

A UN Office on Drugs and Crime report last year blamed high-level collusion and corruption for the rise, while activists across the border in Thailand say the crop substitution programs for poor farmers have not been successful.

The military-ruled nation, meanwhile, has become a hub for methamphetamine production, with convoys of high-tech trucks ferrying chemicals and mobile laboratories under the cover of Myanmar's dense jungle, experts say.