A bomb killed at least 11 people on Monday on a crowded bus in Pakistan's western city of Quetta, capital of a province racked by years of separatist violence.
The bomb exploded as the bus was bound for the city suburbs, carrying dozens of passengers home from work, police official Abdul Waheed Khattak said.
Baluchistan province has seen almost a decade of separatist violence against government personnel and security forces as well as non-Baluch ethnic groups.
Security forces have, in turn, carried out a security crackdown that Baluch activists say has resulted in thousands of disappearances and hundreds of extrajudicial killings.
No group immediately claimed responsibility for the attack on Monday.
The bomb was probably planted on the roof of the vehicle and set off through a timed detonator, Khattak said.
"This is a cowardly act that has targeted innocent people," said Sarfaraz Ahmed Bugti, Baluchistan's home minister. "We are fighting against terrorism here. And we will keep fighting until the last terrorist is killed."
At least one child was among the dead, Bugti said.
Baluchistan chief minister Abdul Malick said at least 21 people were injured and a state of emergency had been declared at the city's hospitals.
Baluchistan has also seen major attacks by the banned Sunni group Lashkar-e-Jangvi, which wants to impose a Sunni theocracy in U.S.-allied Pakistan by stoking Sunni-Shi'ite violence.
Lashkar has in the past bombed religious processions during the Shi'ite mourning month of Muharram, which is currently under way, and shot civilians.
Such attacks have raised doubts about the feasibility of a new economic corridor Pakistan wants to build with billions of dollars of Chinese investment.
The much-vaunted project, announced when Chinese President Xi Jinping visited Pakistan in April, envisages an eastern and western route, with the latter passing through Quetta to Gwadar port in the south.