Two U.S. service members and a U.S. employee were killed on Friday in eastern Afghanistan. The International Security Assistance Force on Saturday said the incident is under investigation. No other information was available. Elsewhere a so-called friendly fire incident between NATO troops and the Afghan army left four Afghan soldiers dead and seven wounded. <br/><br/>The provincial governor's spokesman Shahidullah Shahid the incident occurred early on Saturday morning in the Wardak Province in central Afghanistan. Shahid said an incident caused the exchange of gunfire between troops of the International Security Assistance Force and members of the Afghan National Army. ISAF members said they are investigating the incident and working with Afghanistan's defense ministry to determine what happened.