Military operatives surrounded the building to rescue the children and teachers held hostage on Tuesday, December 16, 2014.
“In CMH (Combined Military Hospital) there are around 60 and there are 24 dead in Lady Reading (hospital),” Pervaiz Khattak, chief minister of the province where Pehsawar is located, told local television channels.
Khattak, said 84 children had been killed.
It was not immediately clear whether some or all of the children were killed by the gunmen or in the ensuing battle with Pakistani security forces trying to gain control of the building.
Outside, helicopters hovered overhead and ambulances ferried wounded children to hospital.
An unspecified number of children were still being held hostage in the school, a provincial official said, speaking some three hours after the attack began.
The Pakistani Taliban, who are fighting to topple the government and set up a strict Islamic state, have vowed to step up attacks in response to a major army operation against the insurgents in the tribal areas.
They have targeted security forces, checkpoints, military bases and airports, but attacks on civilian targets with no logistical significance are relatively rare.