Afghanistan's opium poppy cultivation this year is up by a third, the UN's drugs agency said Tuesday, in its first report on the issue since the hardline Taliban took power in 2021.

The country is the world's biggest producer of poppies, the source of sap that is refined into heroin, and in recent years production and exports have boomed.

The United Nations Office on Drugs and Crime (UNODC) said prices have soared after the Taliban's ban in April on poppy cultivation.

This year's harvest was largely exempted from the decree, UNODC said.

The UN drugs agency said cultivation in Afghanistan rose by 32 percent to 233,000 hectares (580,000 acres) over the previous year, making the 2022 crop the third largest area cultivated since monitoring began in 1994.

The only years that had a higher cultivation area were 2018 and 2019.

The 2022 poppy crop was also "the most profitable in years", according to the Vienna-based UNODC.

The income made by farmers from opium sales more than tripled from $425 million in 2021 to $1.4 billion in 2022, the report said.

Afghan farmers will now decide around early November whether to plant opium poppy for next year and how much to grow despite the ban, the agency said, adding they are "trapped in the illicit opiate economy".

"The current high opium prices provide an additional incentive for farmers to risk cultivating opium poppy, despite the ban by the de facto authorities," the report said.

The harvest however declined to 6,200 tonnes, or 10 percent less than in 2021, after a drought at the start of the year decreased opium yields.

Afghanistan has a near monopoly on opium and heroin, accounting for 80 to 90 percent of global output, according to the UN.

The Taliban previously banned production in 2000, just before the group was overthrown by US-led forces in the wake of the September 11 attacks.

The United States and NATO forces tried to curb poppy cultivation during their two decades in Afghanistan by paying farmers to grow alternative crops such as wheat or saffron.

Yet according to experts their attempts were thwarted by the Taliban, who controlled the main poppy-growing regions and received hundreds of millions of dollars from the trade.