The incident took place on the Ghor-Herat highway in Brak Khana area of Ferozkoh, the provincial capital, this morning.
An eyewitness, Haji Mohammad, told Pajhwok Afghan News two individuals in military uniforms stopped a vehicle carrying passengers from Herat to Ghor.
He said the uniformed men opened fire at the vehicle, killing six passengers and snatched two others. Women and children were among the passengers but they escaped unhurt.
Police spokesman Mohammad Iqbal Nizami said three people were killed and two others wounded in the shooting. The victims belonged to the same tribe.