A Taliban suicide bomber blew himself up in a mosque packed with worshippers during afternoon prayers on Monday in the high-security zone in Pakistan's restive northwestern Peshawar city, killing at least 61 people and wounding more than 150 others, mostly policemen, officials said.
The powerful blast occurred inside the mosque in the Police Lines area around 1.40 pm when worshippers, which included personnel of the police, army and bomb disposal squad - were offering the Zuhr (afternoon) prayers.
The bomber who was present in the front row blew himself up, causing the roof to collapse on the worshippers, officials said.
Capital City Police Officer (CCPO) Peshawar Muhammad Ijaz Khan said 61 people have been killed in the blast.
He said that 300 to 400 police officials were present in the area at the time of the blast. "It is apparent that a security lapse occurred," he told the media.
At least five sub-inspectors and the mosque's prayer leader Maulana Sahibzada Noorul Amin were among the dead.
Lady Reading Hospital officials said more than 150 people were injured.
The Tehreek-e-Taliban Pakistan (TTP), known as the Pakistani Taliban, claimed responsibility for the suicide attack, saying it was part of a revenge attack for slain TTP commander Umar Khalid Khurasani who was killed in Afghanistan in August last.
A police official said that a portion of the mosque collapsed and several people were believed to be under it.
"We are currently focused on the rescue operation. Our first priority is to safely retrieve the people buried under the debris," in-charge Rescue operation Bilal Faizi said.
The bomber entered the highly secured mosque inside police lines where four layers of security were in place.
Provincial Police chief Moazzam Jah Ansari said they are investigating the blast and how the bomber entered the highly fortified mosque.
He expressed apprehensions that the bomber might have been residing in the police lines before the blast as there are family quarters too inside the police lines.
The headquarters of the Peshawar Police, Counter-Terrorism Department (CTD), Frontier Reserve Police (FRP), Elite Force and telecommunications department are also located near the blast site.
Prime Minister Shehbaz Sharif and Army chief General Asim Munir dashed to Peshawar to review the relief and rescue operation.
The premier along with the Army chief also visited the Lady Reading Hospital in Peshawar and inquired about the health of the injured. Interior Minister Rana Sanaullah and other officials were also present.
The Prime Minister summoned an emergency meeting where the preliminary probe report was presented.
Briefing the prime minister, IGP Ansari said he was unaware of where the bomber had come from and how he managed to enter the police lines.
Superintendent of Police (Investigation), Peshawar, Shazad Kaukab, whose office is close to the mosque, told the media that the blast occurred when he just entered the mosque to offer prayers. He said he luckily survived the attack.
The collective funeral of 27 victims was offered at police lines in the evening.
Earlier, Prime Minister Sharif strongly condemned the attack, saying the attackers behind the incident "have nothing to do with Islam".
"Terrorists want to create fear by targeting those who perform the duty of defending Pakistan," he said and vowed that the sacrifices of the blast victims will not go in vain. "The entire nation is standing united against the menace of terrorism."
He also said that a comprehensive strategy will be adopted to counter the deteriorating law and order situation in the restive Khyber Pakhtunkhwa and the federal government will help provinces in increasing their anti-terrorism capacity.
Foreign Minister Bilawal Bhutto Zardari also condemned the attack, saying "terrorist incidents before the local and general elections were meaningful".
Khyber Pakhtunkhwa Governor Haji Ghulam Ali condemned the blast and urged the people to donate blood for the injured, saying that it would be a "huge favour for the police".
The bodies and injured were shifted to the Lady Reading Hospital, officials said.
An emergency has been declared in the hospitals of Peshawar. The hospital has appealed to citizens to donate blood for the victims.
Security has been beefed up in other major cities, including Islamabad, after the Peshawar blast. In Islamabad, security at all entry and exit points of the capital city has been increased and snipers have been deployed at "important points and buildings".
Caretaker Chief Minister Azam Khan condemned the attack and offered condolences to the bereaved families.
He announced one day of mourning on Tuesday.
The national flag will fly half-mast over all main buildings in the province.
Former prime minister Imran Khan strongly condemned the terrorist attack on the mosque.
"My prayers and condolences go to the victims' families. It is imperative we improve our intelligence gathering & properly equip our police forces to combat the growing threat of terrorism," the Pakistan Tehreek-e-Insaf tweeted.
Last year, a similar attack inside a Shia mosque in the Kocha Risaldar area in the city killed 63 people.
The TTP, set up as an umbrella group of several militant outfits in 2007, called off a ceasefire with the federal government and ordered its militants to stage terrorist attacks across the country.
The group, which is believed to be close to al-Qaeda, has been blamed for several deadly attacks across Pakistan, including an attack on army headquarters in 2009, assaults on military bases, and the 2008 bombing of the Marriott Hotel in Islamabad.
In 2014, the Pakistani Taliban stormed the Army Public School (APS) in the northwestern city of Peshawar, killing at least 150 people, including 131 students. The attack sent shockwaves across the world and was widely condemned.