A spokesman for the provincial governor confirming the report said, the aid workers belonged to a non-governmental organization (ACTED).
Provincial security chief Nabi Jan Mullah Khel said, unknown gunmen stopped the vehicle which was carrying the employees of the NGO, and opened fire on them.
Another person has also been injured following the attack, local officials said adding that all the victims were local employees of ACTED non-governmental organization who were working on a government-backed literacy project.
No group including the Taliban militants has so far claimed responsibility behind the incident.
ACTED, the Agency for Technical Co-operation and Development is a French based non-governmental organization (NGO), with global operations in Central Asia, Europe, Latin America, South Asia, Middle East and Africa.
ACTED is among the largest non-governmenal organizations in Afghanistan which has been active in the country since 1993, and mainly operates in the North, Northeastern and Central areas of Afghanistan.