The incident took place in Maiwand district late Thursday evening after an IED planted by Taliban militants went off, killing at least seven people including two women.
Provincial governor spokesman Jawid Faisal confirming the report said at least three others were also injured in the explosion.
Mr. Faisal further added that the incident took place around 7pm local time after the vehicle of the civilians struck with the improvised explosive device.
He said the victims of the incident were all members of a single family, and were on their way to attend an engagement ceremony of one of their relatives when the incident took place.
No group including the Taliban militants has so far claimed responsibility behind the incident.
This comes as United Nations Assistance Mission in Afghanistan (UNAMA) earlier said that civilian casualties had increased by 23 percent, and blamed militant groups for majority of the civilian deaths in Afghanistan.
According to UNAMA at least 1,319 civilians were killed and 2,533 others were injured during the first six months of the year, which shows an increase of 23 percent as compared to the similar period last year.