The death toll in the devastating suicide attack at a mosque inside police headquarters in Peshawar shot up to 100 on Tuesday, with 221 people injured, reported 24NewsHD TV channel.

The dead included a number of police officers including DSP Arab Nawaz and five sub-inspectors. The prayer leader of the mosque was also among the killed.

Khyber Pakhtunkhwa Caretaker Chief Minister Azam Khan has announced a one-day mourning over the mosque tragedy with national flag flying at half-mast on government buildings. He said the death toll has now risen to 100 with 221 injured.

The Tehreek-e-Taliban Pakistan (TTP) 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 year.

A frantic rescue mission continued the whole night at the mosque, which had an entire wall and some of its roof blown out by the suicide hit.

"Many policemen are buried under the rubble," said Peshawar police chief Muhammad Ijaz Khan, who estimated between 300 and 400 officers usually attended prayers.

Bodies were still being pulled Tuesday from the wreckage of the mosque blast. Overnight, at least nine bodies were recovered as rescuers sifted through the rubble of the mosque's collapsed wall and roof.

"This morning we are going to remove the last part of the collapsed roof so we can recover more bodies, but we are not hopeful of reaching any survivors," Bilal Ahmad Faizi, a spokesperson for the Rescue 1122, told AFP.

Muhammad Asim Khan, a spokesman for Lady Reading Hospital in Peshawar, said that 83 people had been killed, with the death toll rising as more bodies arrived from the scene.

The deadly suicide attack inside a highly sensitive police headquarters on Monday, prompting the government to put the country on high alert.

The attack happened during Zuhr prayers in Peshawar, close to former tribal areas along the Afghan border.

Bloodied survivors emerged limping from the wreckage, while bodies were ferried away in ambulances. "It's an emergency situation," Muhammad Asim Khan, a spokesman for the Lady Reading Hospital in Peshawar, said.

Shahid Ali, a policeman who survived, said the explosion took place seconds after the imam started prayers. "I saw black smoke rising to the sky. I ran out to save my life," the 47-year-old told AFP.

During the night, several men were seen trapped in the wreckage, visible through cracks in the concrete.

"We have given them oxygen so that they don't have problems in breathing," said Bilal Ahmad Faizi, a spokesperson for the Rescue 1122.

At least 27 of the killed police officers were later buried after a prayer ceremony with coffins lined up in rows and draped in the national flag. They were laid to rest with a guard of honour, a police official said.

The police headquarters in Peshawar is in one of the most tightly controlled areas of the city, housing intelligence and counter-terrorism bureaus, and is next door to the regional secretariat.

Countrywide high alert

Provinces around the country announced they were on high alert after the blast, with checkpoints ramped up and extra security forces deployed, while in Islamabad snipers were deployed on buildings and at city entrance points.

"Terrorists want to create fear by targeting those who perform the duty of defending Pakistan," said Prime Minister Shehbaz Sharif in a statement.

Officers said the blast came from the second row of worshippers, with investigators were probing the possibility of a suicide attack.

Shahid Ali, a policeman who survived, said the explosion took place seconds after the imam started prayers.

"I saw black smoke rising to the sky. I ran out to save my life," the 47-year-old told AFP. "The screams of the people are still echoing in my mind."

Reporter Mansoor Hussain

With inputs from AFP.