Shafi Ullah, the deputy commissioner of Peshawar, the provincial capital of Khyber Pakhtunkhwa, confirmed the increase in casualties and told reporters that 57 injured people remain hospitalized, 10 of whom are in critical condition.
Earlier, Muhammad Asim, a spokesman for Lady Reading Hospital in Peshawar, while speaking to Anadolu, put the number of casualties at 83.
Nearly 100 injured have been discharged from the hospital, he added.
On Monday, a suspected suicide bomber blew himself up during midday prayers at the mosque within the Police Headquarters in Peshawar.
Tehreek-e-Taliban Pakistan (TTP), a conglomerate of several militant groups, has denied involvement in the attack on its propaganda website.
According to city police chief Muhammad Ijaz Khan, the attack was a suicide bombing as police recovered the head of the bomber from the spot.
Several people were buried under the debris after most parts of the mosque building collapsed, so the rescue operation continued through the night.
The deceased included several senior police officers and the prayer leader.
Defense Minister Khawaja Asif told the local Geo TV channel that the suspected bomber was standing in the front row of the mosque and blew himself up as soon as the prayers began.
"As soon as the imam (prayer leader) began praying, there was a deafening explosion, which tossed me into the air and threw me away," Mohammad Mushtaq, a police officer who got injured in the blast, told reporters at the hospital.
In neighboring Afghanistan, the Taliban administration condemned the bombing, calling it "against the teachings of Islam."
In a statement, the Afghan Taliban Foreign Ministry also expressed sympathy to the families of the deceased and injured.
Meanwhile, the Khyber Pakhtunkhwa government is observing a day of mourning across the province on Tuesday.
"In view of the two most unfortunate incidents of capsizing of a boat full of children at Tanda Dam, Kohat on 29-01-2023 and the terrorist attack at Police Lines, Peshawar on 30-01-2023, causing irreparable loss of human lives, the Provincial Government with a deep sense of grief and sorrow announces Tuesday as a day of mourning throughout the Province of Khyber Pakhtunkhwa," said a notification.
"The National Flag of Pakistan shall fly at half-mast throughout the Province of Khyber Pakhtunkhwa," it added.
4 militants killed
Four militants were killed in a joint intelligence-based operation by security forces and police against terrorists in the districts of Swabi and Dera Ismail Khan in Khyber Pakhtunkhwa province.
According to police, the joint operation was carried out after the Counter-Terrorism Department (CTD), police, and intelligence agencies received information about the presence of militants in Hind village in Swabi on Monday.
The militants opened fire on security forces and police, but two of them blew themselves up and the third surrendered, they said, adding that two police officers were also injured during the operation.
Separately, two militants were killed in the Dera Ismail Khan district during an encounter with security forces in the Loni area on Monday.
A search operation was conducted in the area based on a tip-off about the presence of terrorists, the local Dawn newspaper reported citing unnamed sources, who also said a huge amount of weapons were also recovered from the possession of the slain terrorists.