The incident took place Friday as Afghan security forces were clearing a village of Taliban elements, Salam Afghan, Helmand police spokesman, told AFP.
“In the strike, 16 Afghan policemen were killed including two commanders,” he said.
“Two other policemen were wounded,” he added.
Omar Zwak, Helmand provincial governor spokesman, confirmed the strike and gave the same account.
It occurred in Gereshk district in Helmand, large parts of which are under Taliban control.
“During a US-supported (Afghan security) operation, aerial fires resulted in the deaths of the friendly Afghan forces who were gathered in a compound,” a Nato mission in Afghanistan said in a statement..
“We would like to express our deepest condolences to the families affected by this unfortunate incident,” it said, adding there would be a probe into what happened.
The US is the only foreign force in the coalition conducting airstrikes in Afghanistan.