Police in Pakistan are investigating a suspected suicide bombing that killed at least 57 people at a festival held in honour of the Prophet Muhammad.
The attack is thought to be the worst in Pakistan in years
The attack, targeting tens of thousands of worshippers at an evening prayer service in Karachi, was the deadliest on Pakistan's Sunni Muslims for years.
Angry crowds later went on the rampage in the city, accusing the police of failing to provide adequate security.
Hundreds of troops were on high alert as funerals took place on Wednesday.
Three days of mourning have been declared in Sindh province.
Moderate Sunni Muslim leaders were among those killed in the attack in Karachi's Nishtar Park - on a wooden stage where religious leaders were sitting.
The authorities say they have no clue as to who might be behind the blast, which sparked fears of a cycle of tit-for-tat attacks. No group has said it carried out the bombing.
The BBC's Zaffar Abbas in Karachi says it is being described as one of the worst incidents of suicide bombing against Pakistan's majority Sunni Muslim community.
He says the people who faced the brunt of the blast were moderate Sunnis who have mostly kept away from sectarian conflict.
Officials first said they thought at least two suicide bombers were involved after finding two severed heads at the blast site, but made clear on Wednesday they had revised that to one.
"We identified one of the heads as belonging to a sound technician working near the stage, and now believe only one suicide bomber was involved," Karachi police chief Niaz Siddiqui told the Associated Press news agency.
Officials condemned the attack and urged people to remain calm.
Authorities shut schools and petrol stations in the city, amid fears of further unrest.
However, the atmosphere at funerals has been sombre rather than violent and so far the situation has remained under control, the BBC's Zaffar Abbas reports from the city.
Anger at the attack earlier spilt over into violence as hundreds of enraged worshippers took to the streets.
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 explosion took place at what was believed to be the biggest of such events being held in Pakistan.
The attack happened as people took part in evening prayers
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, our correspondent says.
"The blast shook the earth. It was like hell," Mohammad Ehtesham, 70, told Reuters news agency.
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.