Pakistani police officers and volunteers gather at the wreckage of a bus destroyed in a bomb blast in Quetta on June 15, 2013.
Heavily-armed gunmen have attacked a hospital in the southwestern Pakistani city of Quetta, killing at least four people and injuring several others.
The siege came hours after an explosion on a bus killed at least 11 female university students in the capital city of the volatile Balochistan Province on Saturday.
Security sources say the gunmen used heavy weapons and explosive devices to attack the different sections of the hospital complex where the students were being treated.
The militants armed with grenades were positioned on rooftops and exchanged fire with members of the security forces and police commandos, said local residents and eyewitnesses.
Some local media reports say nearly 20 people have been killed in the bus explosion and fresh attacks on the medical center in the troubled city, adding that the death toll is expected to rise as some of the injured are said to be in critical condition.
Meanwhile, Pakistani Prime Minister Nawaz Sharif has issued a statement strongly condemning the bomb attack.
No group has claimed responsibility for the attack, but police officials put the blame on pro-Taliban militants or some Baloch militant groups that have carried out similar assaults in the past.
In the past few months insurgents have destroyed dozens of gas pipelines and power towers in different parts of Balochistan.
Some Baloch militant groups say they want greater political autonomy and a share of the province’s natural resources.
Thousands of Pakistanis have lost their lives in bombings and other militant attacks since 2001, when Pakistan entered an alliance with the US in the so-called war on terrorism.
Thousands more have been displaced by the wave of violence and militancy sweeping across the country.
JR/SS
This article originally appeared on: Press TV