Wahidullah Jumazada, a spokesman for provincial governor, said that the civilians were travelling in a car when it was struck by a roadside bomb in Dasht-e-Pirka area on road to Jaghatu district.
None of the passengers in the car survived the blast, he said.
There was no immediate claim of responsibility for the bombing.
Civilians continue to bear the brunt of war in Afghanistan despite intensified peace efforts.
At least 1,213 civilians were killed while 1,744 more were wounded in the conflict in Afghanistan in the first half of 2020, according to the United Nations.