Fourteen passengers were forced to offload from a bus on Makran Coastal Highway in Balochistan's Ormara area and shot dead by unidentified gunmen early on Thursday.
Pakistan Navy personnel were among the martyred in the attack, which took place near Bozi Top, a Pakistan Navy spokesperson said.
The attackers, who numbered around two dozen, were wearing camouflage uniforms, provincial home secretary Haider Ali told AFP.
They "stopped buses on the Makran Coastal Highway and gunned down 14 people", he said, adding that the four vehicles were travelling to Karachi from the coastal town of Ormara.
Provincial home minister Mir Zia Langov said a full-scale investigation had been launched into the attack and to track down the gunmen, who he said had fled the scene.
"Such incidents are intolerable and we will not spare the terrorists who carried out this dastardly attack," he said.
The bodies were shifted to a nearby health facility in Ormara.
The attack came less than a week after 21 people, including eight Hazara, were killed and 48 others injured in a suicide blast in Quetta's Hazarganji sabzi mandi.
PM seeks report on incident
Prime Minister Imran Khan strongly condemned the killings in a statement from his office and sought a report on the incident.
Expressing his sympathies with the families of the victims, the premier directed the concerned authorities to make every possible effort to identify and bring the perpetrators of the barbaric act to justice.
President Dr Arif Alvi condemned the terrorist attack and expressed profound grief and sorrow at the loss of precious human lives in the incident. He also prayed for eternal peace of the departed souls and forbearance of the bereaved families.
Balochistan Chief Minister Jam Kamal also strongly condemned the incident and said, "Terrorists are killing innocent people on the agenda of anti-state elements."
"It is a conspiracy to create hurdles in the development of Balochistan," the chief minister added.
Information Minister Fawad Chauhdry earlier today said there appeared to be an "organised pattern" in the attack on members of Hazara community, Tehreek-e-Taliban Pakistan (TTP) in Hayatabad and the shooting on the passengers of the bus.