Gunmen fatally shot 23 passengers after identifying them and taking them from buses, vehicles and trucks in one of the deadliest attacks in restive southwestern Pakistan, police and officials said Monday.

The killings occurred overnight in Musakhail, a district in Balochistan province, senior police official Ayub Achakzai said. The attackers burned at least 10 vehicles before fleeing the scene.

President Asif Ali Zardari and Interior Minister Mohsin Naqvi in separate statements called the attack barbaric" and vowed that those who were behind it would not escape justice.

The attack came hours after the outlawed Baloch Liberation Army separatist group warned people to stay away from the highways, but there was no immediate claim of responsibility.

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 group and others demanding independence from the central government in Islamabad. Islamic militants also have a presence in the province.