The incident took place in Postay Syah area of Maiwand district in the morning.
Samim Khplwak, a spokesman for provincial governor, said that all the victims belonged to those who were in the truck that was severely damaged.
According to the official, the driver of the trailer escaped the site after the incident.
However, he said police were seeking to arrest the criminal.
Narrow roads, lack of traffic signals and driver negligence are factors behind most of the traffic accidents in Afghanistan.