Police said the blast was caused either by a suicide bomber or an explosive device which went off when the mosque was at its fullest on Friday afternoon in the center of Shikarpur, a city in Pakistan’s southern province of Sindh.
Radical Sunni Islamist groups often target mosques frequented by minority Shi’ites, whom they see as infidels.
Earlier this month, six people were killed and 17 wounded by a suicide bomber outside a Shi’ite mosque in the city of Rawalpindi, also after Friday prayers.
“We are trying to ascertain the nature of the blast,” said Shikarpur police chief Saqib Ismail Memon. “A bomb disposal squad is examining the scene.”
Saeed Ahmed Mangnejo, head of the regional civil administration, told Reuters that the death toll had reached 49.
In chaotic scenes that followed the blast, part of the mosque collapsed after the explosion, burying some of the wounded under rubble. Bystanders pulled people from the debris and piled them into cars for the journey to hospital.
Locals said there were not enough ambulances and the army later sent additional vehicles to transport people to hospitals.
The atmosphere was tense in Shikarpur after the explosion, with shops boarded up and crowds of emotional residents massing outside hospitals.
“The entire city is in lockdown and there is tension in the air. There is a heavy police presence and the Rangers are patrolling the city,” said Pariyal Marri, a local resident.
“THEY ARE OUR ENEMIES”
Jundullah, a splinter group of Pakistan’s Taliban which last year pledged support for the Islamic State group based in Syria and Iraq, claimed responsibility.
“Our target was the Shia mosque … They are our enemies,” said Fahad Marwat, a Jundullah spokesman. He did not elaborate.
Majlis Wahdat-e-Muslimeen, a Shi’ite organization, has called for a province-wide strike on Saturday in protest.
Sain Rakhio Merani, a regional police official, said the blast was probably caused by a bomb, although Pakistani television quoted some residents as saying they saw a man wearing a suicide vest.
The attack came as Pakistan tries to adopt new measures to tackle Islamist extremists following a massacre of 134 children last month at an army-run school in the northwestern city of Peshawar.
The government has pledged to crack down on all militant groups, reintroduce the death penalty, set up military courts to speed convictions and widen its military campaign in lawless tribal areas.
Yet Pakistan’s religious minorities, among them Ahmadis, Christians and Hindus, say the government is doing little to alleviate their daily struggle against humiliation, discrimination and violence.
Shi’ites make up about a fifth of Pakistan’s mainly Sunni population of around 180 million. More than 800 Shi’ites have been killed in attacks since the beginning of 2012, according to Human Rights Watch.
(Additional reporting by Syed Raza Hassan in Islamabad and Saud Mehsud in Dera Ismail Khan; Writing by Maria Golovnina; Editing by Mike Collett-White)