The banned Lashkar-e-Jhangvi claimed responsibility for yesterday's attacks, saying they were carried out in retaliation for a raid against the group by security forces.
Fourteen students of the Sardar Bahadur Khan Women's University and four nurses of the Bolan Medical Complex were among the dead.
The attack on the women's university bus was carried out by a woman suicide bomber, Express News channel quoted security sources as saying.
Twenty-two women were injured by the powerful blast.
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Reports said the bus was assigned for students from a nearby neighbourhood dominated by the Shia Hazara community, which has been the target of several attacks by the LeJ.
When the victims of the attack were taken to the nearby Bolan Medical Complex, the hospital was stormed by a group of heavily armed militants.
One militant blew himself up near an operation theatre while the others fired indiscriminately and took people hostage.
The militants targeted the hospital as several senior police and civil officials, including the police chief and Chief Secretary of Balochistan, were leaving the building after enquiring about the victims of the first attack.
Four militants were either killed or blew themselves up while one was captured by security forces, who also freed 35 hostages.
Chief Secretary Babar Yaqoob Fateh Muhammad confirmed 25 people had died and about 50 were injured in both attacks.