A gun and bomb attack near a women's university, and ensuing siege at a nearby hospital, in Quetta has killed at least 24 people, including 11 female students, and wounded dozens of others, police and local officials say.
The first explosion happened on a bus near the campus of the Sardar Bahadur Khan Women's University, with a bomb hidden in the vehicle, reports said.
The second blast struck the casualty ward of the Bolan Medical Complex, and firing continued in the aftermath. At least eight unidentified gunmen are reported to have taken positions in the hospital, and have so far killed at least three security personnel who were attempting to resecure the facility and three nurses, local officials said.
"They are several in number, we are still facing resistance from them, and people are stranded inside the hospital. We are trying our best to rescue the people," said Jan Mohammed Bulaidi, spokesman for Balochistan's new chief minister, who took office last Sunday.
Zubair Mahmood, the city police chief, described the bombing targetting the bus as having been carried out by an "improvied explosive device". The bomb exploded after the students had boarded and the bus was leaving the university.
"We are investigating if it was a remote controlled bomb," the police official said.
Another police official, Fayyaz Sumbal, added that the bus caught fire after the explosion and many students were critically wounded.
Siege at hospital
Authorities say that three security personnel and Abdul Mansoor Khan, the deputy commissioner of Quetta, were among those killed at the hospital, Al Jazeera's Kamal Hyder reported. So far, at least 36 people have been injured in both attacks, he said.
"This particular sitaution is still very fluid. We are told that the security forces have now surrounded that compound, there is exchange of fire, that the people who are inside with weapons are said to be firing at security forces and perhaps some kind of a hostage situation is developing with the doctors, patients and attendants all stuck inside the hospital," he reported from the Pakistani capital Islamabad. "A cordon [has been formed] outside the hospital with security forces on the ground and helicopters in the air to try and monitor this particular situation."
Quetta is the capital city of Balochistan province, and regularly witnesses violence on a large scale.
Earlier on Saturday in the town of Ziarat - some 120km from Quetta - a rocket attack by unknown attackerskilled a policeman and gutted a historic summer retreat used by Pakistan's founder Muhammad Ali Jinnah.
Since the start of the year, more than 300 people have been killed in attacks by sectarian, ethnic and anti-state groups in Quetta.