At least 13 worshippers were killed and around 50 others injured in a suicide bomb attack on a packed Shiite mosque in the Pakistani city of Karachi during prayers, officials said.
"The death toll can rise further," an interior ministry official told AFP on Friday.
The bomb was detonated among rows of worshippers in the Haideri Mosque, adjacent to the southern port city's historic Sindh Madarsahtul Islam School, provincial government advisor on security Aftab Sheikh told AFP.
The mosque belonged to the minority Shiite Muslim sect while the school was founded by Pakistan's founding father Mohammad Ali Jinnah.
Baluchistan provincial government home ministry advisor Aftab Sheikh said it had been confirmed the attack was carried out by a suicide bomber. "I can confirm it now," he said in a statement on a private television channel.
Panic spread in the area and volunteers rushed casualties to hospital in cars, auto-rickshaws and on motor bikes, witnesses said.
The blast destroyed part of the mosque roof and shattered windows, witnesses said.
"A fireball was seen emerging from the site of the blast," injured Mushtaq Ali told AFP. "I was hurt by a splinter."
Sheikh said some 50 people had been wounded and several had their limbs severed. Blood spattered on the floor and severed limbs were seen lying in the mosque. Many of the injured were reported in critical condition.
Police cordoned off the mosque as angry people from both Sunni and Shiite communities chanting slogans against the blast gathered outside the mosque.
Angry youths hurled rocks, damaging several official vehicles.
A state of emergency has been declared in the main Civil Hospital where more than 50 people have been admitted with head and abdomen injuries. Many were suffering from burns.
Appeals for blood were made through public address systems fitted on private vehicles.
Weeping relatives of the victims were crying and embracing each other amid scenes of chaos at the hospital, witnesses said.
Hospital officials said eight of the bodies had been identified.
"It could be a suicide attack," police officer Gul Hameed Sammo told AFP at the Civil Hospital. One or two bodies were "charred and badly mutilated," Sammo said.
Rizwan Edhi, a senior official of a private ambulance service said "several people died in my arms."
"It's a barbaric act. We cannot say who is behind it, but this act is a sheer barbarism," Shiite senator Abbas Komeili said.
President Pervez Musharraf "strongly condemned the attack" his office said.
"He has directed the administration to carry out a thorough investigations and reiterated the government's resolve to eliminate terrorism."
Musharraf has also directed the provincial government "to extend all possible relief to the injured."
The attack follows a car bombing on Monday which killed three Chinese engineers in the coastal town of Gwadar, some 450 kilometres (280 miles) west of Karachi.
Scores of Pakistanis have been killed in suspected sectarian violence over the past year.
Some 48 people were killed in an attack on a Shiite religious procession in the southwestern city of Quetta in March.
A bloody attack on a Shiite mosque in Quetta also left 48 people dead and sparked violent protests in July.
Shiites form 20 percent of the country's 145 million population. Sectarian violence involving militants from the two countries have claimed more than 4,000 people over the past several years across the country.