By Ian MacWilliam
BBC correspondent in Kabul
Post-Taleban Afghanistan is mass producing heroin again
The head of the United Nations Office on Drugs and Crime has arrived in Afghanistan to visit projects connected with Afghanistan's illegal narcotics industry.
Antonio Maria Costa will visit two of Afghanistan's main poppy growing areas in the north east of the country.
Afghanistan is the source of about three quarters of the world's supply of opium which is made from the poppy flower.
The north of Afghanistan has had a bumper crop this year as good winter snows have watered the fields of brilliant red, purple and white poppies.
Dr Costa has arrived on a regular visit to inspect the work of the UN Office on Drugs and Crime, which is trying to reduce poppy cultivation here and the illegal export of opium and its derivative, heroin.
Afghanistan supplies most of the opium and heroin consumed in Europe and in Afghanistan's neighbours, Pakistan and Iran.
Dr Costa is meeting the Afghan president, Hamid Karzai, in Kabul and he will also travel to Badakhshan and Nangrahar in the north and east, two of Afghanistan's main poppy growing provinces.
President Karzai's government has banned poppy cultivation, but eradicating the lethal flower is difficult because it is one of the few sources of income in the impoverished areas where it is grown.
A farmer can make several thousand dollars from a poppy harvest, whereas growing wheat or other crops would provide barely a subsistence living.
Opium has long been used as a traditional medicine in Afghanistan, but heroin consumption has not been a significant problem.
But a recent survey by the UN suggested that the use of opium, heroin and other narcotics in Kabul is also on the rise.