UNITED NATIONS — Opium production in Afghanistan has increased by 34 percent over the past year, and the country is now the source of 93 percent of the heroin, morphine and other opiates on the world market, according to a report by the United Nations' anti-drug agency.

"Afghanistan's opium production has thus reached a frighteningly new level, twice the amount produced just two years ago," said the U.N. Office on Drugs and Crime's annual opium survey, released Monday in Kabul.

"Leaving aside 19th-century China," the report noted, "no country in the world has ever produced narcotics on such a deadly scale."

The surge in opium production has frustrated U.S. and NATO military commanders, who believe that the trade plays a major factor in funding a Taliban insurgency that has become increasingly deadly over the past two years. Commanders also believe that the involvement of public officials in the drug trade has undermined Afghans' confidence in their government.

Neighborhoods of mansions have gone up in Afghan cities in recent years, with many of the houses financed by drugs. The newfound wealth in a country that remains desperately poor has spurred resentment among many Afghans who blame their government and the international community for not doing more to give people an economic alternative to poppies.

Seven years ago, the Taliban leader Mohammad Omar banned the cultivation of opium poppies — but not their export — on the grounds that growing them violated the principles of Islam. But the report says that Taliban leaders have reversed their position and are now using drug profits to buy weapons and logistical equipment and to pay the salaries of their militia.

The vast majority of Afghanistan's opium poppies are grown along the border with Pakistan, in five southwestern provinces with a Taliban presence, according to the report. Helmand, a Taliban stronghold that accounts for half of the country's opium, "has become the world's biggest source of illicit drugs, surpassing the output of entire countries like Colombia (coca), Morocco (cannabis), and Myanmar (opium) — which have populations up to 20 times larger."

"The Afghan situation looks grim, but it is not yet hopeless," the drug agency's executive director, Antonio Maria Costa, said in a statement. He cited evidence that several provinces in central and northern Afghanistan had actually eradicated their opium fields. The northern Afghan province of Balkh has seen a decline in opium cultivation from 17,000 acres to zero.

The report attributes the drop to a combination of economic incentives and security guarantees that "have led farmers to turn their back on opium."