“The blast happened after a number of lawyers and some journalists had gathered at the hospital following the death of the president of the Balochistan Bar Association in a separate shooting incident early this morning,” said Balochistan Home Minister Sarfraz Bugti.
Police and hospital sources had initially said at least 35 people were killed. The death toll is expected to rise even higher.
Graphic video footage from the scene was published on social media showed bodies strewn on the ground, some still smoking, among pools of blood and shattered glass as shocked survivors cried and comforted one another.
Pakistani police have said they suspect the bomb was detonated by a suicide attacker.
No one immediately claimed responsibility for the attack.