Logar province spokesman Din Mohammad Darwesh said the attack took place in the provincial capital of Puli Alam.
Another eight people were wounded, he added.
NATO also said that insurgents killed one of its service members in eastern Afghanistan. It provided no other details or the nationality of the victim, but most troops in the east are from the United States.
So far five foreign soldiers have been killed this month, including four Americans, for a total of 108 this year. Violence has spiked in recent months as insurgents have launched attacks to retake lost ground as foreign troops withdraw.