A NATO airstrike killed five Afghan soldiers and wounded at least eight others early Thursday in the eastern province of Logar.
A spokeswoman for the U.S.-led international forces in Afghanistan said the troops were accidentally killed during a military operation.
She said an investigation is ongoing to determine the cause of the incident, and sent condolences to the families of those killed.
It was not immediately clear what weapons were used to carry out the airstrike or what target was hit.
Provincial officials in Logar said they will meet later Thursday to determine their official response.
The strike comes amid a low point in ties between the United States and Afghan President Hamid Karzai, who has criticized airstrikes that kill Afghans.
President Karzai, who is on an official visit to Sri Lanka, has not commented on the strike.
U.S. officials say if Karzai does not agree soon to a long-delayed deal on a lasting American military presence, all U.S. troops will be pulled from the country in December.
Karzai is set to leave office following elections on April 5.