Peshawar: A powerful suicide blast ripped through a crowded Shia mosque during the Friday congregation here in northwest Pakistan, killing at least 57 people and wounding nearly 200 others, in one of the deadliest attacks in the restive province, bordering Afghanistan.

A rescue official said the blast occurred at a Jamia mosque in Qissa Khwani bazaar area in Peshawar when the worshippers were offering Friday prayers.

No group immediately claimed responsibility for the blast in Peshawar, the provincial capital of Khyber-Pakhtunkhwa which borders Afghanistan. However, the Islamic State and sectarian militant groups have claimed responsibility for the deadly attacks targeting Shias in the past.

Mohammad Asim, a spokesperson for Lady Reading Hospital (LRH), confirmed that at least 57 people were killed while 194 were injured in the blast.

Khyber-Pakhtunkhwa government spokesman Barrister Mohammad Ali Saif said the explosion was a suicide bombing. He added that two terrorists were involved in the attack.

Talking to the media, Peshawar SSP Operations Haroon Rasheed Khan said the explosion was a suicide blast.

There were two attackers but only one of them was a suicide bomber, he said.

An eyewitness identified a person as dressed in black as the suicide bomber, saying he entered the mosque, shot and killed the security guard first and then fired five to six bullets.

"After that, he quickly entered the [mosque's] main hall and blew himself up in front of the pulpit. Following this, there were bodies and injured people lying everywhere," the eyewitness told Geo News.

An emergency has been declared in the hospital and doctors on leave were summoned. 

Officials said the condition of some of the injured is stated to be critical. 

Capital City Police Officer Peshawar Ijaz Ahsan said two attackers tried to enter the mosque and fired at the policemen standing guard. One policeman was killed while the other was critically injured, he said. 

The blast occurred following the firing incident, he added.

President Arif Alvi condemned the blast and expressed grief over the precious lives lost. 

Prime Minister Imran Khan strongly condemned the Peshawar blast while Interior Minister Sheikh Rashid Ahmed sought a report of the incident from the Chief Secretary and IG of the province.

Khyber-Pakhtunkhwa Chief Minister Mahmood Khan condemned the blast and vowed to bring the perpetrators of this heinous act to justice.

He said targeting people in a place of worship is an inhuman and cruel act and directed authorities to ensure the best medical care to the injured.

He has convened an emergency meeting at Chief Minister's House to review the overall security situation in the province, bordering Afghanistan. 

"Heart-wrenching terrorist incident in Peshawar in which so many precious lives have been lost. Words can't adequately condemn the sheer brutality. Terrorism continues to remain our foremost national challenge. Prayers & condolences are with the bereaved families!" PML-N President and Leader of the Opposition in the National Assembly Shehbaz Sharif tweeted.