At least 57 people have died in a suspected suicide bombing at a ceremony to mark the anniversary of the Prophet Muhammad's birth in southern Pakistan.
The attack happened as people took part in evening prayers
More than 80 people were injured when the blast ripped apart a wooden stage where religious leaders were sitting.
Tens of thousands of Sunni Muslims had been taking part in evening prayers in Karachi's Nishtar Park at the time.
Angry crowds later went on the rampage in the city, accusing the police of failing to provide adequate security.
Three days of mourning has been declared.
The attack was condemned by Shia leader Allama Hassan Turabi as well as President Pervez Musharraf and Prime Minister Shaukat Aziz.
Officials confirmed the death toll had risen to 57.
He told the BBC the attack appeared to have been carried out by a suicide bomber.
Initial reports suggested the bomb had been planted under the wooden stage, but Mr Sherpao said "investigators have found no crater in the ground under the stage".
"People sitting on the stage were killed which suggests the bomb was carried by someone on the stage," the minister added.
No-one has claimed responsibility for the explosion at what was believed to be the biggest of such events being held in Pakistan.
Karachi has a history of sectarian and ethnic violence, but this is the first time in decades that a religious gathering celebrating the Prophet's birthday has been targeted, the BBC's Zaffar Abbas in Pakistan says.
"The blast shook the earth. It was like hell," Mohammad Ehtesham, 70, told Reuters news agency.
Sunni Muslim leaders taking part in the ceremony were believed to be among the dead.
"I saw body parts everywhere. I saw people collecting body parts and putting them in ambulances," another witness said.
An emergency has been declared at the city's hospitals. Off-duty doctors and paramedics have been called in and appeals are being made for blood.
Twenty-four bodies were reported at one hospital alone.
'Nothing is working'
Anger at the attack spilt over into violence as hundreds of enraged worshippers took to the streets accusing the authorities of failing to provide adequate security.
They hurled rocks at the security forces who fired shots in the air to try and disperse the crowd. A petrol station as well as cars were burned.
The bomb attack sparked angry scenes in Karachi
Sherbanoo Raza told the BBC her mother had been in her car when it was set alight, along with up to 30 others nearby.
"My mother panicked, she was terrified. She went up to a friend's house nearby," she said.
"It's not even safe enough for her to cross the road and get a cab home. Nothing is working."
The event had been organised by the Sunni organisation Jamaat-e-Ahle Sunnat.
The group draws support from the same Sunni community that lost 29 women and children in a stampede during prayers also marking the Prophet's birthday in a Karachi Islamic centre at the weekend.