Security officials piled the narcotics, which were seized in 2008, into a massive oven in a Soviet-era metal smelting plant before setting them ablaze.

Mountainous Uzbekistan is increasingly becoming a transit country for drugs coming from Afghanistan and Tajikistan, James Callahan told reporters.

Since the US-led invasion in 2001, Afghanistan has become the world’s leading heroin producer, placing an increasing burden on law enforcement officers in its Central Asian neighbours.

"The problem of being a transit country... is that it increases the incidence of drug abuse among Uzbek citizens as well as the problem of HIV, which is connected to injected drug use," Callahan said.

Nonetheless, the UNODC is pleased with the efforts of Uzbek law enforcement bodies to fight against illegal drug trafficking, he said.

Uzbek security service officials said 3.5 tonnes of narcotics, including almost 1.5 tonnes of heroin, were seized in 2008.

Since 1994 Uzbekistan has publicly destroyed 42 tonnes of drugs, according to officials.