The incident took place around 10:00 am local time in Sancharak district after the suicide bomber targeted a former Jihadi leader.
Provincial governor Mohammad Zahir Wahdat said the former Jihadi leader Rahim Ayoubi survived the attack unhurt but four members of his family were killed.
He said the victims include two sons and two nephews of Ayoubi and another member of his family was wounded.
Wahdat further added that Ayoubi had left his family members inside his vehicle as he was visiting a cemetary when the suicide bomber targeted the vehicle.
No group including the Taliban militants has so far claimed responsibility behind the incidet.
Ayoubi was a member of Jamiat-e-Islami party of Afghanistan and was a key member of the party in Sar-e-Pul province as he was waging fight against the anti-government armed militant groups.
Taliban militants and insurgents belonging to the other militant groups are actively operating in a number of Sar-e-Pul province and often carry out insurgency activities.