The attack on the Pakistani labourers took place some 20 kilometres from the emerging port city of Gwadar in Balochistan province that forms the southern hub of the China-Pakistan Economic Corridor (CPEC).
"All the labourers were shot at close range," said senior levies official Muhammad Zareef, adding that the shooters were travelling on a motorcycle. The levies are a paramilitary force that oversees security in Balochistan where police jurisdiction is limited to major urban centres.
Gwadar's deep-water port is the exit point for a planned route from China's far-western Xinjiang region to the Arabian Sea.
Nadeem Javaid, who advises Prime Minister Nawaz Sharif's government and works closely on the CPEC programme, told Reuters earlier in the week that the Gwadar-Xinjiang corridor should be operational from June next year.
He said Pakistan expects up to 4 percent of global trade to pass through it by 2020.
Balochistan, however, has long faced security concerns. Separatist terrorists in the province have waged a campaign against the central government for decades, demanding a greater share of the gas-rich region's resources.
Pakistan's military created an army division in 2015, believed to number more than 10,000 troops, specifically to protect CPEC projects and Chinese workers.
The men killed and wounded on Saturday had been working for the provincial government at two separate construction sites on three kilometres apart along the same road. Two labourers wounded in the shootings were taken to hospital where one of them died from his injuries, Zareef said.
The roads the labourers were working on are not specific CPEC-funded projects, but they are part of a network of connecting roads that are part of the corridor.
No group has admitted responsibility for the shootings but past attacks in the region have been carried out by separatists who view construction projects as a means to take over their land.
The shootings come a day after a suicide bomber targeting a Pakistani senator killed 26 people and injured 40, Baluchistan Home Minister Sarfraz Bugti said.
Friday's attack was claimed by ISIS via its Amaq news agency.