A bomb has killed at least 15 people at evening prayers in a Shia mosque in Pakistan's southern city of Karachi.
Today's attack is the latest in a string of terrorist attacks to hit the southern Pakistan city of Karachi.
Doctors said they had counted 15 dead and at least 55 wounded, a dozen critically, while wailing men and women searched in the darkness for relatives believed buried in rubble under the cracked dome of the city centre mosque.
An angry crowd outside the mosque compound set fire to vehicles and prevented police from approaching the scene, letting through only ambulances.
Karachi had feared fresh inter-Muslim sectarian violence after the killing on Sunday of Mufti Nizamuddin Shamzai, a radical Sunni preacher, and thousands of police were on duty at the city's mosques in anticipation of a backlash.
A suicide bomber killed 24 people and wounded 125 in an attack on another Shia mosque in Karachi on May 7, but police were unsure whether this too was a suicide bomb attack.
Ishratul Ibad, the governor of Sindh province, appealed for calm, telling Geo Television: "This is a planned act and those behind it are very organised."
Information Minister Sheikh Rashid Ahmed told the same news channel that President Pervez Musharraf planned to take serious action to restore order in the city.
The Ali Raza Imam Bargah mosque, the target of the bomb, was less than a mile away from where Shamzai, a pro-Taliban cleric who called for "jihad", or holy struggle, against the United States, was killed.
One worshipper, a man called Saddiqan, said he had been on his way into the mosque when the explosion knocked him off his feet. "I saw two dead bodies without limbs lying on the ground," he said.
Anger among the several hundred people gathered outside the bombed mosque spilled over and a mob set fire to a nearby petrol station, a police van and a private car.
"I can hear gunshots and the angry crowd is torching cars and tyres, while a gas station has already been burnt," a Reuters correspondent at the scene said.
While the latest bombing smacked of domestic sectarianism, ingrained hatred for the United States surfaced along with grief and anger among the crowd and many chanted "Down with America".
As the violence at the scene worsened, police fired tear gas to disperse the mob, adding to the stench of burning rubber.
A police officer said four people were wounded by gunshots in a street a few hundred metres from the bombed mosque.
Elsewhere in the city, youths in Shia neighbourhoods blocked roads, pelted vehicles with rubbish and shouted anti-American slogans.
The city will be braced for more violence tomorrow, when relatives of the victims are due to bury their dead.