A bomb blast targeting Shiite Muslims in south-western Pakistan on Saturday killed at least 64 people and wounded 180, police said, dpa reports.
The powerful explosion demolished a two-storey building at a busy market near a neighbourhood inhibited by ethnic Hazaras in the town of Quetta, said police chief Mir Zubair Mahmood.
"The victims include children and women," Mahmood told reporters during a news conference. "The death toll might rise because several people are in critical condition."
Mahmood said up to 80 kilogrammes of explosives had been packed in a water bowser. It was not immediately clear how the blast was triggered.
Television footage showed rescuers sifting through piles of bricks and concrete in search of survivors, as authorities feared people might be trapped underneath the rubble.
No group immediately claimed responsibility for the blast. Banned Sunni extremist group Lashkar-e-Jhangvi has carried out several deadly attacks against Shiites in recent months.
Prime Minister Raja Pervez Ashraf condemned the bombing and reiterated Pakistan's resolve to fight terrorism.
"Terrorists will not be able to subdue our will through such dastardly acts," Ashraf said in a statement.
The regional government announced a day of official mourning on Sunday, while Shiite groups called for a strike.
Quetta is the capital of Balochistan province, which was placed under federal rule last month after two bombings killed at least 86 people, mostly Shiites.
In a report issued this month, Human Rights Watch said that more than 400 Shiite Muslims were killed in "targeted attacks" across Pakistan in 2012.
It said the government had failed to protect Shiites or take action against those responsible for the attacks.