But the oppressive regime is turning a blind eye to – and even profiting from – the manufacture and sale of crystal methamphetamine both in and outside the country.

Crystal meth, or ice, is considered one of the most addictive and harmful drugs in the world, but not in North Korea.

"It's not treated as serious abuse, and can even be prescribed as medicine," University of Technology Sydney associate professor Bronwen Dalton told nine.com.au.

The prevalence of drug use in North Korea is very common, according to International Christian University in Tokyo's Stephen Nagy.

"Most South Korean studies based on interviews with defectors say that about 30 percent of the population are using some kind of drug," he told nine.com.au.

"These drugs are used to deal with the exhausting labour conditions, for 'recreation' and escapism."

There's many reasons the regime turns a blind eye to the drug trade, Dr Nagy said.

"First, it manufactures drugs for export to earn hard currency. It excepts some of the surplus to filter into the population," he said.

"Second, the stimulates keep the fatigued population energetic enough to continue working to meet the regime's demands including agricultural production etc."

"Drugs are easier to come by than rice," one refugee told the Database Centre for North Korean Human Rights.

"Unless you're a simple organism, you do drugs," said another.

A bridge leading from the Chinese town of Dandong to the North Korean town of Sinuiju. (AAP)

North Korea is now a significant exporter of illegal drugs, with crystal meth from the country flooding the market in the Chinese border province of Liaoning.

"If you're a drug addict in China, you are usually addicted to heroin," Dr Dalton said.

"But in that province it's crystal meth."

Drug smuggling into China is as simple as crossing the Yalu River, often across the bridge to Dandong.

Chinese authorities only check a fraction of the hundreds of trucks that cross the border every day, meaning smugglers can skirt narcotics laws as easily as they can skirt other sanctions placed on North Korea .

Drug use is illegal in North Korea, but the ostensibly socialist regime has no qualms about lining their pockets with drug bribes.

"It's excused particularly if methamphetamine results in earning foreign currency," said Dr Dalton.

"The regime is on the take in regards to any economic activity."

South Korea-based Daily NK reported last month that universities and pharmaceutical factories were being used to make meth.

"North Korean state companies and merchants have been waiting for the export markets to re-open ever since sanctions began having a significant impact in February this year," a source within North Korea told the news site.

"But now trade has been shut down for the coal exporters due to the country’s missile launches, and they are turning to drug production and smuggling as a replacement."

Meanwhile, Dr Nagy said North Korea was taking advantage of diplomacy laws to smuggle drugs into Southeast Asia.

Ambassadors and diplomats do not have to have their bags checked by customs, meaning heavy-hitters from the Pyongyang foreign office may be working as drug mules.

"Drugs can be smuggled out through diplomatic pouches but that would only be small scale and provide hard cash to diplomats abroad," Dr Nagy said.

A Chinese truck driver who drives goods to North Korea walks between full-loaded trucks in Dandong. (AAP)

North Korean diplomats have also been tied to the smuggling of elephant ivory, counterfeit cigarettes, pirated DVDs and gold.

"There's no such thing as organised crime in North Korea that doesn't involve the government," US State Department expert David Asher told Vice in 2014.

"Crime is disobeying the leadership.

"If they find somebody going around the senior leadership, that person gets whacked."

North Koreans have even been caught smuggling drugs to Australia. In 2003 Australian special operations soldiers boarded cargo ship the Pong Su on suspicions it was involved in a massive heroin operation.