According to security sources, unknown gunmen opened fire on their vehicle near Darga Mandi area of Ghulam Khan tehsil in the area.
A total of four militants were killed.
The identity of rest of the three militants could not be confirmed yet.
The attackers fled from the scene while panic gripped the area after the incident.
The local residents shifted the bodies to the hospital.
Bhittani had served as the acting TTP chief after Hakeemullah Mehsud's death and also headed the Taliban supreme shura (council).
North Waziristan is one of seven regions in Pakistan's Federally Administered Tribal Area governed by tribal laws.
The area is a safe haven for TTP militants and al-Qaeda operatives.