Heavily-armed men on Saturday blew up a bus carrying female students and then attacked a hospital treating survivors of the blast.

At least 29 people were killed in total and dozens of others injured in the attacks.

Pakistani Interior Minister Chaudhry Nisar said that four gunmen were also killed during the siege of the emergency ward of the hospital that lasted for several hours and ended when the security forces stormed the building.

Nisar said that the security forces also freed 35 people who were taken hostage by the militants.

"As casualties were being brought to the hospital terrorists had taken position inside the hospital building," Nisar told reporters.

"They opened fire on administration and police officials who arrived at the hospital. One…bomber blew himself up in the hospital," he added.

The outlawed Pakistani terrorist group Lashkar-e-Jhangvi claimed responsibility for Saturday’s massacre in Quetta.

The group was founded in 1996 by Riaz Basra after he broke away from Sipah-e-Sahaba Pakistan over differences with his superiors.

On February 16, a bomb attack targeting Shia Muslims in the main bazaar of Quetta killed about 90 people, including women and children, and injured 200 others. According to the police, most of the victims were Hazara Shias.