At least 30 civilians were killed and 40 injured in an air strike conducted by the Afghan security forces, backed by US air support, in eastern Afghanistan, officials said on Thursday.

The attack on Wednesday night was aimed at destroying a hideout used by Islamic State (IS) militants, but it accidentally targeted farmers near a field in Wazir Tangi area of Khogyani district in Nangarhar province, three government officials told Reuters.

Sohrab Qaderi, a provincial council member in eastern Nangarhar province, said a drone strike killed 30 workers in a pine nut field and at least 40 others were injured.

The defense ministry in Kabul confirmed the strike conducted by Afghan and US forces was aimed at fighters belonging to the IS, but refused to share details of civilians casualty caused by the attack.

Attaullah Khogyani, a spokesman for the provincial governor of Nangarhar, confirmed the air strike.

“The government is investigating the incident, so far nine bodies were collected from the attack site near a pine nut field.”

US forces in Kabul were not immediately available for a comment.

Malik Rahat Gul, a tribal elder in Wazir Tangi said the air strike happened at a time when tired workers, mainly daily wage earners, had gathered near their tent after harvesting pine nuts in a field nearby.

“The workers had lit a bonfire and were sitting together when a drone targeted them,” said Gul.

Earlier in May, US air strikes killed 17 policemen by mistake during a battle with insurgents in the country’s southern Helmand province.

In the last year, the number of US air strikes has risen, most often in response to Afghan requests for assistance, but also in an intensified campaign against the militant Islamic State group, who are mostly headquartered in eastern Afghanistan.

A higher frequency of US air stri­kes has led to more civilian deaths, according to UN reports. A quarterly estimate by the UN issued recently said more civilians were killed by Afghan and US forces than by insurgents in the first months of 2019.