A suspected suicide attack near a mosque in the city of Peshawar in northwestern Pakistan left dozens of people dead and many more injured, local authorities said on Monday.
Police and hospital officials said at least 33 people had lost their lives and some 150 were injured. The sensitivity of the location has caused the government to place the country on a heightened state of alert over terrorism.
There are fears that the death toll will continue to rise as emergency services clear the rubble. Many of those taken to hospital were listed in "critical condition."
"A portion of the building had collapsed and several people are believed to be under it," police official Sikandar Khan said told Reuters news agency.
Footage from government broadcaster PTV showed police, firefighters, and residents working to remove debris from the site and carrying the wounded out on their shoulders. Rescuers brought in heavy machinery to help with the effort.
Meena Gul, a 38-year-old police officer who was at the mosque at the time, said he could hear screams and cries after the suicide bomber detonated.
What do we know about the blast?
The explosion came as worshippers gathered for daily prayers. Initial estimates suggested that at least 260 people had been inside at the time.
The blast shook the city's government district on Police Lines Road. Authorities said many of the victims were believed to be police officers.
Pakistani Prime Minister Shahbaz Sharif condemned the bombing, promising "stern action" against those responsible.
He made it clear that terrorist attacks "have nothing to do with Islam."
"Terrorists want to create fear by targeting those who perform the duty of defending Pakistan," Sharif said.
His office also said he would visit the site in Peshawar.
Local police told reporters that initial evidence suggested a terror attack. Later, Prime Minister Sharif officially termed the blast a suicide bombing.
Interior Minister Rana Sanaullah announced an inquiry would soon follow into how it was possible for a suicide bomber to successfully penetrate multiple layers of security.
In a post on Twitter, former Pakistani Prime Minister Imran Khan referred to the incident as a "terrorist suicide attack." Khan added, "It is imperative we improve our intelligence gathering & properly equip our police forces to combat the growing threat of terrorism."
Taliban claims responsibility
As with similar violent incidents in the recent past, the attack was claimed by the Pakistani Taliban.
Peshawar in the capital of the Khyber Pakhtunkhwa province bordering Afghanistan.
Pakistani journalist Yusra Askari told DW that while "the situation on the border has been relatively calm the last couple of months," the "Taliban recently promised revenge" for several attacks it blames on Islamabad.