A statement from the US-led coalition says the soldier died after coming under direct fire by enemy forces today.
The coalition, known as the International Security Assistance Force, provided no other details or the nationality of the killed soldier.
Afghan insurgents have increased attacks in recent months, intensifying a campaign to regain territory as foreign forces draw down ahead of a full withdrawal at the end of 2014.
Today's death brings to eight the number of coalition deaths so far this month. Last Tuesday, six US soldiers died when their Black Hawk UH-60 went down during a mission in Zabul, southern Afghanistan.