A powerful bomb explosion at a busy mosque in Pakistan's northwestern city of Peshawar has killed at least 33 people and wounded 150, according to officials.
A hospital official said many of the casualties were police officers who had gathered in the mosque for afternoon prayers.
The mosque is located in the vicinity of a police housing block, and there were reportedly some 260 worshippers inside when the blast occurred.
"Many policemen are buried under the rubble," said Peshawar police chief Muhammad Ijaz Khan, who estimated between 300 and 400 officers usually attended prayers at the mosque.
"Efforts are being made to get them out safely," he said.
Bloodied survivors emerged limping from the wreckage, while bodies were ferried away in ambulances as the rescue operation continued.
"It's an emergency situation," Muhammad Asim Khan, a spokesman for the main hospital in Peshawar told AFP, putting the death toll at 33.
Khyber Pakhtunkhwa governor Ghulam Ali put the death toll at 28 and 150 wounded, most of them policemen.
According to police, the casualty toll is likely to mount as many people are still lying beneath the debris.
Footage from government broadcaster PTV showed security forces and residents scrambling to remove the rubble and carrying those injured in the blast on their shoulders for medical treatment.
"A portion of the building had collapsed and several people are believed to be under it," police official Sikandar Khan was quoted as saying.
No group immediately claimed responsibility for the bombing in Peshawar, the capital of the Khyber Pakhtunkhwa province bordering Afghanistan, but observers say it could be the handiwork of the Terrorist group Pakistan Tehreek-e-Taliban (TTP)
Some reports said the brother of slain TTP commander Umar Khalid Khurasani had called it revenge for the killing of Khurasani.
Khurasani, a top commander of the outfit, was killed in a bomb blast in August last year in southeastern Afghanistan, with the group blaming Pakistani security and intelligence agencies.
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Bombing kills nearly dozen in Pakistan’s Peshawar
Pakistan's Prime Minister Shehbaz Sharif strongly condemned the attack, reiterating the national resolve and unity to eliminate terrorism from the country.
In a statement, he said the killing of Muslims while they worshipped was in violation of Islamic teachings and that the attack on a mosque showed the perpetrators had nothing to do with Islam.
“The killers of innocent people will be made an example. The whole nation including the institutions was united against terrorism,” he remarked.
In past years, the TTP militants have been involved in multiple terrorist attacks, including targeted bombings and killings of members of religious communities and security officials across the violence-hit country.
On December 16, 2014, the group mounted an attack against Peshawar’s Army School, where more than 150 people, mostly children, were killed, one of the deadliest massacres in the South Asian country's history.