The killings occurred overnight in Kusakhail, a district in Balochistan province, a senior police official Ayub Achakzai.Â
The attackers burned at least 10 vehicles before fleeing the scene.
Pakistani Interior Minister Mohsin Naqvi condemned the deadly attack. (EPA PHOTO)
Interior Minister Mohsin Naqvi called the attack "barbaric" and vowed that those who were behind it would not escape justice.
"The armed men also not only killed passengers but also killed the drivers of trucks carrying coal," said Hameed Zahir, the deputy commissioner of the area where the attack occurred.
At least 10 trucks were set on fire after their drivers had been killed, he added.
The attack came hours after the outlawed Balochistan Liberation Army separatist group warned people to stay away from the highways.
In a statement, the group said its fighters had targeted military personnel travelling in civilian clothes, who were shot after being identified.
The separatists in Balochistan have often killed workers and others from the country's eastern Punjab region as part of a campaign to force them to leave the province, which for years has experienced a low-level insurgency.
Most such previous killings have been blamed on the outlawed Baluchistan Liberation Army and other groups demanding independence from the central government in Islamabad. Islamic militants also have a presence in the province.
with Reuters