A security officer at a checkpoint on a roadside in Helmand on Aug. 26. Afghan officials said Sunday that a friendly-fire incident in the southern province killed 11 Afghan police officers. (Watan Yar/EPA)

An airstrike by international forces killed at least 11 members of Afghanistan’s counternarcotics police force and wounded four others in southern Afghanistan on Sunday, according to Afghan officials.

The attack unfolded in the Garmsir district of Helmand province during an anti-drug operation involving government forces, officials said, but details were not immediately available. Helmand is a hotbed of Afghanistan’s thriving poppy production.

If the reports are confirmed, the strike would be among the deadliest friendly-fire incidents in recent years.

“Seems it was an attack without coordination,” said Najib Danesh, a spokesman for the Interior Ministry.

A media report placed the number of dead at 28, but Danesh said he was unable to confirm the figure.

Karim Attal, the chief of Helmand’s provincial council, said the dead included people unaffiliated with government forces.

“Apart from the police, 25 nongovernment people, who were armed and were among the vehicles of the police, were also killed,” Attal said. “A team is probing to determine what these people were doing.”

Col. Brian Tribus, a spokesman for U.S. forces in Afghanistan, denied international involvement in the incident and referred questions to the Afghan Interior Ministry.

“There were no strikes conducted by U.S. or NATO forces in Helmand Province on 6, September,” he said in a statement. “U.S. forces conducted kinetic strikes in Maiwand District, Kandahar Province on September, 6th to eliminate threats to the force. There were no Afghan Security Forces injured in the US strike in Maiwand, Kandahar on 6, September.”

Sunday’s airstrike is the second instance of friendly fire in as many months. In July, a U.S. airstrike involving an Apache helicopter killed eight Afghan soldiers at a military outpost in Logar province. At the time, officials said the area, south of the capital, was considered a stronghold of Taliban insurgents.

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