The Taleban make profits from opium in southern strongholds
A surge in the cultivation of opium and coca in rebel-held areas threatens to undermine recent progress in drug control efforts, says a UN report.
Afghanistan had a record opium harvest last year and coca leaf production in Colombia increased 27%, according to The World Drug Report 2008.
The UN Office on Drugs and Crime (UNODC) says most regions where these drugs are grown are held by insurgents.
It adds that increases in supply from these areas could fuel addiction rates.
UNODC chief Antonio Costa says drug control has made impressive achievements in recent years - but insurgent involvement threatens that progress.
He said some of the world's biggest drug-producing regions - in Afghanistan, Colombia and Burma - were out of the control of the central government.
Drug trafficking, he added, was also undermining national security - especially in parts of Central America, the Caribbean, Mexico, and West Africa.
In Afghanistan, the record 2007 harvest meant the world's illegal opium production had almost doubled since 2005.
About 80% of that cultivation took place in five southern provinces, where Taleban insurgents profit from drugs, the report says. Elsewhere in the country, opium growing is reported to be in decline.
"Greater stability and higher economic assistance are getting rid of opium in many provinces of Afghanistan," Mr Costa said.
"In the southern areas, controlled by the Taleban, counter-narcotics and counter-insurgency must be fought together."
In Colombia, the regions where most coca is grown are also under the control of insurgents - mainly the Revolutionary Armed Forces of Colombia (Farc), who are believed to be at their weakest point in years, following the death of their long-time leader, Manuel Marulanda, in March.
Although coca leaf cultivation increased in Colombia, Bolivia and Peru in 2007, production has remained the same, because of lower yields.
"In the past few years, the Colombian government destroyed the large-scale coca plots by means of massive aerial eradication," Mr Costa said.
"It was an unquestionably successful campaign against armed groups and drug traffickers alike. In the future, with the Farc in disarray, it may become easier to control coca cultivation."
The BBC's Bethany Bell, in Vienna, says the report shows world cannabis and amphetamine markets were stable. But it said there has been a big increase in seizures of amphetamines in Saudi Arabia.
No death penalty
In terms of drug use, the report said that less than 5% percent of all adults took drugs.
Lower prices could mean higher drug use in developing countries
Illegal drugs, it said, were responsible for about 200,000 deaths a year worldwide, but that compared with 7.5 million who died as a result of tobacco and alcohol.
But Mr Costa warned against complacency and said everyone needed to be more proactive as major increases in drug supply from Afghanistan and Colombia could drive addiction rates up, because of lower prices and higher purity of doses.
He said weak governments could not face the onslaught of powerful drug barons, or drug addiction.
"The attack must be pre-empted by technical assistance, better drug prevention and treatment, and more co-operative law enforcement," he said.