The Sunni extremist outfit Lashkar-e-Jhangvi announced on Sunday that it had sent a female suicide bomber to strike the bus in Quetta, capital of the restive Balochistan province, killing 14 students from a women's university near a Shiite neighborhood on Saturday.

About 90 minutes later, a follow-up attack on the hospital treating survivors left at least 11 dead and led to a prolonged gun battle between security forces and militants occupying part of the building.

"The suicide attack on the bus was carried out by one of our sisters," said Abubakar Siddiq, a spokesman for Lashkar-e-Jhangvi. "She boarded the student bus and blew herself up. Then we carried out a second suicide attack at the hospital and our fighters killed several people. We did this because security forces killed our fighters and their wives in Kharotabad."

Troops fought gunmen who seized parts of the Bolan Medical Complex in Quetta after the initial explosion. The standoff lasted for several hours and ended when security forces stormed the building, freeing 35 people who had been taken hostage, Interior Minister Chaudhry Nisar told reporters on Saturday.

Quetta's head of police operations, Fayaz Sumbal, said those killed in the hospital explosion included a senior government official who had arrived to assess the situation.

Attack on historic building

Earlier on Saturday, suspected separatists killed a policeman and gutted a historic summer retreat once used by Pakistan's founder, Muhammad Ali Jinnah, in a hill town in the province.

Saturday's attacks were the heaviest since bombings in Quetta at the start of the year claimed almost 200 lives and came only a week after Prime Minister Nawaz Sharif took office.

Baluchistan is a vast province bordering Iran and Afghanistan and home to large deposits of copper and gold.

mkg/slk (AFP, AP)