Taliban fighters have destroyed fields of opium poppies in eastern Afghanistan this spring, the first time since 2001 the hardline Islamist group is known to have clamped down on the cultivation of a drug that provides a big part of its funding.

While the insurgents appear to have dug up a relatively small area of poppies in a remote area near the border with Pakistan, the move was so unusual it won a chorus of praise from the Afghan government and international organisations, whom the Taliban consider their enemy, as well as senior clerics.

"They just did what the constitution ordered," said Wasifullah Wasifi, a spokesman for the provincial governor in Kunar, where the eradication took place.

"The provincial governor really appreciates what the insurgents did. From the perspective of Islam it is forbidden and a crime to grow drugs," Wasifi said, adding that nearly a hectare had been destroyed by the Taliban in the province's Manawara district, in addition to a far larger amount eradicated by the government.

The country representative of the UN Office on Drugs and Crime in Afghanistan, Jean-Luc Lemahieu, confirmed that the Taliban had uprooted poppy fields in Kunar, and said he hoped the "rare event" might presage a stronger approach to controlling drug production.

"We welcome this new approach and would hope that this is not a one-time exception but that the Taliban, and others alike, would take a principled stance against the narcotics business," he said.

Afghanistan has for years produced the vast majority of the world's opium, with only a brief break in 2001 when the Taliban government, which had previously relied on the crop to bolster its coffers,unexpectedly dug up most of the country's poppy fields.

But opium production has flourished since the group was toppled by US-backed forces in 2001, even though it has been widely condemned by clerics as un-Islamic.

Villagers in the Manawara district were warned at the start of the sowing season not to plant poppies, said district governor Habib Rahman Mohmand.

"The Taliban leadership in Kunar sent down an order to the ordinary people that they should not grow drugs, or the crop would be destroyed," Mohmand said. "Around 20 days ago the Taliban groups came and destroyed it."

Mohmand said he believed it had been done on the order of a powerful regional commander, Zia al-Rahman. The order, however, was the result of pressure from tribal elders and religious scholars in Kunar who considered the production of drugs un-Islamic, he told the Guardian.

A local Taliban fighter who said he was involved in the eradication confirmed that the decision had come from the top commander, for religious reasons.

"It was an order from Zia al-Rahman. We went to the site to destroy the drug fields, and there were two widows who were growing drugs to feed their families because they had no husbands, so I didn't destroy their land," said the militant.

"But when Zia al-Rahman heard, he got upset, and said: 'We don't care who the owners are, this is a religious order.' So I went to the site again and destroyed the land of the widows."

In 2011, the farm-gate value of opium production in Afghanistan more than doubled from the previous year to $1.4bn (£885m) according to Reuters.

Funds flow to insurgents and corrupt members of the government. The crop can also be a key source of income for poor farmers, who insurgents sometimes rely on for food, shelter, recruits or other support.

"Over the past 10 years the Taliban have generally been pragmatic about poppy. They have not been involved in eradication," said Michael Semple, a Harvard academic and expert on the Taliban.

"In the poppy heartland of the south, where the opium trade is important in the rural economy, Taliban commanders deliberately delay the start of the spring fighting so as to allow farmers a chance to complete the opium harvest."

In eastern Kunar, opium production is just a fraction of levels in the Taliban's southern heartland, and the local commanders may have seen a chance to match government eradication programmes with their own claim to moral leadership on drugs production, Semple added.

"In Kunar the acreage planted is much smaller and opium is peripheral to the economy. In eradicating some poppies, local Taliban probably saw an opportunity to pose as a legitimate force."

Kunar residents also said there had been some eradication by the Taliban in two neighbouring districts, although authorities in both areas denied any militant role in clearing poppy fields.

"In Shaygal district in some areas, the government was doing the eradication, and in other areas the insurgents were doing the eradication," said an English teacher, who asked not to be named.

"As an eyewitness I can say the Taliban destroyed a jerib [a fifth of a hectare] of drugs between four and five days ago," said Haji Padshah Jan, an elder from a third district, Sarkani.

**Rahmatullah Qaryab in Kunar and Mokhtar Amiri in Kabul contributed reporting for this story