Gunmen killed 11 people in southwest Pakistan, officials said Saturday, with police searching for suspected separatist militants after migrant labourers were singled out for execution.

Police said six gunmen stopped a bus near the city of Naushki in Balochistan province around 8:00 pm (1500 GMT) on Friday and checked people's ID cards, abducting nine workers from the eastern region of Punjab.

Their bodies were later found two kilometres (1.2 miles) from the highway having been "fired upon at point blank range", senior local police officer Allah Bakhsh told AFP.

The same attackers later fired at a car belonging to a provincial parliamentarian, Bakhsh said. The lawmaker was not in the vehicle, but two people were killed when the car careened into a ditch.

"Police and paramilitary forces started combing the area for the arrest of the attackers," senior Naushki district administration official Habibullah Musakhail told AFP.

"But the attackers have managed to flee the area this time," he said, also confirming the death toll.

Bakhsh said the gunmen "clearly used the modus operandi of Baloch separatists" and "an investigation has been launched to confirm who was behind the attacks".

Ethnic separatists have waged a decades-long insurgency in Balochistan, Pakistan's largest but poorest province, despite an abundance of natural resources.

Militants have in the past targeted ethnic Punjabis and Sindhis from elsewhere in Pakistan, as well as foreign energy firms they believe are exploiting the region without sharing its riches.

Prime Minister Shehbaz Sharif described Friday night's attack as an "incident of terrorism" in a statement and said "facilitators will be punished".

In October last year, gunmen killed six Punjabi labourers who were constructing a private residence.

Late last month, eight Baloch militants were killed as they attempted to storm the offices of a port considered a cornerstone of China's investment in the region.

Two Pakistani soldiers were killed repelling the assault, the military's public relations wing said.

Islamabad's security forces are the most frequent target of separatists, who claim their communities are subject to a regime of extrajudicial killings and disappearances as reprisals for their resistance.