Six NATO troops died and three others were wounded by a vehicle-born explosive device near Bagram Airfield, according to a statement from the international coalition in Afghanistan.
The coalition did not specify the nationalities of the casualties, but US officials told NBC News that American soldiers were among the dead and the wounded.
The officials did not specify the total number of Americans involved in the incident, and further details on the attack were not immediately available.
Bagram is a large US military base north of Kabul, the Afghan capital.
Parwan provincial police chief Gen. Zaman Mamozai told NBC News that a suicide bomber on a motorcycle attacked a convoy of Afghan and Western forces at around 1 p.m. local time.
The Taliban posted a message on Twitter claiming responsibility for the attack.
An attack near Bagram Airfield in September killed one NATO service member.