The Taliban's supreme leader on April 3 ordered a ban on poppy cultivation in Afghanistan, warning that the hardline Islamist government would crack down on farmers planting the crop.

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

"All Afghans are informed that from now on cultivation of poppy has been strictly prohibited across the country," said a decree issued by Supreme Leader Hibatullah Akhundzada. "If anyone violates the decree the crop will be destroyed immediately and the violator will be treated according to the sharia law.”

The fundamentalist group had also banned production in 2000, just before it was overthrown by US-led forces in the wake of the September 11 attacks.

US 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.

However the Taliban controlled the main poppy-growing regions and derived hundreds of millions of dollars from the trade, experts say, although these claims have been refuted by the current regime.

Afghan media reports say production has increased in two southern provinces, Kandahar and Helmand, since the Taliban seized power in August, although data is not available.

Afghanistan accounts for 80 to 90 per cent of global output of opium and heroin, according to the UN. The amount of land planted with poppies hit a record high in 2017 and has averaged around 250,000ha in recent years, roughly four times the level of the mid-1990s.