At least four Israelis, including a pregnant woman, are reported to have been shot dead in the Hebron region.
Their car came under fire from a passing vehicle at the Beni Naim junction on Highway 60.
Security officials describe it as a well-planned ambush. The attackers are said to have paused to confirm that the victims were dead before fleeing.
Security forces and Magen David Adom ambulances rushed to the scene. Palestinian security forces were also told of the attack, which took place just as the Ramadan fast was ending, and are looking into the incident.