The wounded driver, Abdul Khaliq, said he saw assailants on two motorcycles open fire and then flee. He said he was hired by the Bravo Institute of Technology, Peshawar to take the women from the town of Bannu to the town of Mir Ali and back.
The attack drew condemnation from rights activists on social media, with most demanding swift action against those responsible.
Pakistani militants have in recent months stepped up their activities in the region, raising fears they were regrouping in the area, which was a former Taliban stronghold.
Militants also often attack Pakistani troops in the former tribal regions bordering Afghanistan.
The North and South Waziristan districts served as the main base for local and foreign militants until the military secured the regions in 2015.