NATO's International Security Assistance Force says three U.S. troops and a civilian were killed when a NATO helicopter went down in southeastern Afghanistan late on April 8.
An ISAF statement said the cause of the crash in Zabul Province was not known and that an investigation had been launched.
The nationality of the dead civilian was not immediately clear.
A Zabul government spokesman, Mohhamed Jahn Rasuliyar, said it appeared the helicopter went down due to technical problems.
Qari Yusuf Ahmedi, a Taliban spokesman, claimed militants had shot down the helicopter.
The helicopter crashed near the provincial capital Qalat.
compiled from agency reports