KABUL -- The United Nations called Wednesday on Afghan authorities to target corrupt senior officials involved in drug trafficking after a new report said heroin and opium production here hit record levels.

The annual report from the UN's International Narcotics Control Board (INCB), released in Vienna on Wednesday, said heroin production in Afghanistan reached a new high in 2007.

The country also produced 34 percent more opium last year than in 2006 and now accounts for 93 percent of opiates on the world market, it said, reiterating statistics released by the UN Office on Drugs and Crime (UNODC).

"Fresh measures against corrupt officials implicated in illicit drugs activities must be taken," the UNODC's representative in Afghanistan, Christina Oguz, told reporters in Kabul.

"Corruption is a major obstacle to solving the drugs problem in this country," she said.

Oguz said opium was largely turned into morphine and heroin in Afghanistan, especially near the Pakistan border where there were mobile conversion "units" that could be moved around by truck, making them difficult to detect.

"The majority of these laboratories are owned by Afghans ... with very good connections with high-ranking officials within the country," she said.

However hardly any of the chemicals used to turn opium into heroin had been seized by the authorities. They were often disguised as oil or other commodities when smuggled, she said.

"The trafficking of opium and heroin within the country and out of the country is very, very well organized," she said.

"The networks are very powerful because the big drug traders are linked to high officials and to criminal networks outside of Afghanistan."

Smuggling routes were controlled by criminal networks or "terrorists," she said, referring to militants linked to the Taliban movement that is waging an insurgency against the government of Afghan President Hamid Karzai.

Rebels earned money from protecting these routes and also took 10 percent of drugs income from farmers in the south.

"There are clear indications they are involved in processing, trafficking and also take a part of the profit from these trades," she said.

The UNODC representative said the government faced a difficult task in ridding itself of corruption and the drugs trade.

"It is not easy to target corruption when corruption is part of your machinery ... and because of low capacity within government institutions," she said.

Afghanistan's illegal drugs trade is worth about $4 billion, equal to more than half of the legal gross domestic product.