The men were shot dead in Shadi Kaur area of Gwadar district yesterday.
They were identified by officials as residents of Zhob district.
The workers were attacked in the early hours yesterday at a place about 25 km from Pasni town on the coastal highway linking Gwadar and Karachi.
The men were working on the highway when four gunmen on motorcycles lined them up, checked their identity and opened fire.
"A 12-year-old boy, who was spared by the gunmen, gave details of the incident to law enforcement personnel," Naeem Gichki, Assistant Commissioner of Pasni, told Pakistani newspaper Dawn.
Gwadar district police officials said security forces were looking for the killers but no arrest had been made so far.