The insurgents had stormed a poultry farm in the Lasbella district, which is close to Karachi, and kidnapped 11 labourers working at the farm, police said.
They questioned labourers over their ethnicities.
"They blindfolded the nine workers belonging to Punjab province and shot them while setting the two Baluch workers free," they said.
"Later two of the freed labourers reached a local police station and informed the police of what had happened," senior official Bashir Brohi said.
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Chief Minister Balochistan Malik Baloch strongly condemned the killings and directed police to bring the culprits to book.
In a statement he termed the incident as tragic and vowed the perpetrators would be arrested.
This is not the first time that insurgents have targeted labourers and workers from other provinces and killed them.
The insurgents, who are demanding autonomy and greater economic share for the mineral-rich province, have also been targeting government installations and security forces at regular intervals in other parts of the province.
No group has claimed responsibility for the gruesome killings.