Updated

The United Nations says Afghan farmers have increased their opium poppy production by about 18 percent this year, compared to last year.

High prices for the illicit crop overcame government efforts to stamp out the crop, the U.N. said in a report released Tuesday.

Opium sales fund insurgents and criminals in large segments of the country

Afghanistan is the world's largest producer of opium, the raw ingredient in heroin.

The United Nations Office on Drugs and Crime said in the report that the increase in cultivation comes despite increased destruction of poppy fields by the Afghan government.

The report indicated that despite the increase, nature limited the growth. Plant diseases and bad weather cut the potential size of the crop by 36 percent to 3,700 tons.