The probe was launched after reports that nine civilians were killed in a NATO air strike near the town of Lashkar Gah in the
troubled southern province of Helmand on Wednesday.
President Hamid Karzai confirmed that members of foreign forces shot dead unarmed civilians, including eight teenagers, in the northeastern province of Kunar on Saturday.
NATO's International Security Assistance Force (ISAF) has denied the dead were unarmed, and has said that no NATO or US military personnel were involved in the incident.