The Department of Defense in a statement said during a US supported Afghan National Defense Security Force operation, aerial fires resulted in the deaths of the friendly Afghan forces who were gathered in a compound. We would like to express our deepest condolences to the families affected by this unfortunate incident, the statement said. <br/>'<br/>Helmand provincial Governor Hayatullah Hayat said the NATO airstrike hit on Friday and that at least two Afghan commanders died. He said the death toll was expected to rise further because several security force personnel were known to have been in the compound at the time. <br/>'<br/>While much of Helmand province is under the control of the Taliban, the Afghan national security forces have been waging fierce battles to retake territory.