Rescue officials on Tuesday recovered the severed head of the suspected suicide bomber who they believe blew himself up inside a mosque packed with worshippers during the afternoon prayers on Monday in the high-security zone in Pakistan's restive northwestern Peshawar city.

The death toll from the bomb blast rose to 93, with 221 people severely wounded, police officials said, even as rescue operations continued to retrieve the remaining bodies from the debris.

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 suicide 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 Mohammad Aijaz Khan told Geo TV that the blast appeared to be a suicide attack and the head of the suspected bomber was recovered at the site in Peshawar, the capital of Khyber Pakhtunkhwa province.

"It is possible that the attacker was already present in the Police Lines before the blast and that he may have used an official vehicle [to enter]," he was quoted as saying by Geo TV.

Khan added the exact nature of the blast will be known once the rescue operation concludes.

Khyber Pakhtunkhwa's Caretaker Chief Minister Muhammad Azam Khan on Tuesday announced a day of mourning in the province following the attack.

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.

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 has sent shockwaves across the world and was widely condemned.

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