Four people were killed on Monday and 15 injured in a roadside bomb that targeted a police car in south-western Pakistan, a government spokesman said.
Two officers and two civilians were killed, while the injured were mostly civilian pedestrians in the attack in Quetta, the capital of Balochistan province, said Babar Yousafzai, a spokesman for the provincial government.
Officials suspect the Pakistani Taliban of being behind the attack but no group has claimed responsibility.
The Taliban's wing in the country have been conducting attacks since November when they ended a months-long ceasefire with the government.
Balochistan has been volatile for more than a decade since a conflict between the Pakistan government and separatists in the province demanding complete autonomy or a larger share of the province’s gas and mineral resources.
Provincial chief minister Abdul Qudoos Bizenjo condemned the attack and ordered authorities to provide the best possible medical care to the wounded.
The Pakistani Taliban, who are known as Tahrik-e-Taliban (TTP), have claimed responsibility for previous attacks in Balochistan and elsewhere. The militant group is separate from, but allied with, the Afghan Taliban.
The latest attack comes a day after the TTP shot and killed two police officers in Quetta.
One of the assailants was also killed when police returned fire after coming under attack in the city on Sunday night.
The gas-rich south-western Balochistan province straddling the border of Afghanistan and Iran has been a scene of a low-level insurgency by Baloch nationalists for more than two decades.
They initially wanted a share of the provincial resources but later initiated an insurgency for independence.
Last week, Pakistan launched a new nationwide operation to root out armed militants.
"The meeting agreed to launch an all-out comprehensive operation with the entire nation and the government, which will rid the country of the menace of terrorism with renewed vigour and determination," the security committee said last Friday.
