Officials say two Afghan soldiers have been killed in fighting between NATO and Afghan troops in what may have been a friendly fire incident, according to a report of The Associated Press. A Wardak province spokesman, Shahidullah Shahid, says NATO and Afghan soldiers began fighting early Saturday after a misunderstanding following an operation in the Sayed Abad district. A NATO official says the joint force came under fire from unknown assailants and responded, calling in air support. The official says two Afghan soldiers were killed in the incident but it was not immediately clear who fired on them. The official says an investigation is under way.