Over 50 people were also injured in the attack in which Kalashnikov-wielding Taliban suicide attackers stormed the Imamia Masjid Imambargah in the posh Hayatabad area in the city where worshippers had gathered for the Friday prayers, opening fire and exploding bombs in a revenge attack.
Dr Touheed of Hayatabad Medical Complex in Peshawar confirmed that the death toll had risen to 22 after an injured person succumbed to his wounds.
The Tehreek-e-Taliban Pakistan (TTP) claimed responsibility for the attack and warned that it was the first in a series of revenge attacks.
Taliban spokesman Mohammad Khurasani said it was a retaliation to the hanging of the militants by the government following the Peshawar school massacre that claimed 150 lives, mostly students.
More From This Section
Pakistan Prime Minister Nawaz Sharif condemned the mosque attack and promised that militants will be brought to justice.
Pakistan Army launched Zarb-e-Azb in North Waziristan in June last and had so far killed more than 1,600 militants.
The style of yesterday's attack bore a striking similarity to the December 16 Peshawar carnage, in which the gunmen arrived in a car, set it on fire and broke into the building using a back entrance.