Dozens of children slaughtered as Taliban storms Pakistan school

(CNN) -- At least 84 people, most of them children, have been killed after a group of gunmen stormed an army-run school in the Pakistani city of Peshawar.

The Pakistan Taliban -- Tehreek e Taliban Pakistan (TTP) -- claimed responsibility for the attack Tuesday.

Pervez Khattak, chief minister of the northwestern province of Khyber Pakhtunkhwa, said over 80 of the injured are children ranging from 12 to 16 years of age. He added that two of the attackers are now dead -- one blew himself up, while the other was killed by security forces.

Earlier, Shahram Khan, the province's health minister, told CNN that two teachers and an army official had also been killed, while 104 more were wounded.

Hostage situation

The Pakistan military said a rescue operation involving its troops is currently underway at the school, with gunfire still being exchanged.

Khattak said there was an "ongoing hostage situation."

Prime Minister Nawaz Sharif is reportedly on his way to Peshawar, where he will announce a period of national mourning.

In a telephone call to CNN, a spokesman for the TTP, who identified himself as Mohammed Khurrassani, claimed that six suicide bombers entered the school compound with orders to kill older students. He added that "300 to 400 people are under custody of the suicide bombers" and that they are in contact with them.

He added that they will soon release a mobile phone recording and images of the attack.

CNN can not confirm how many people remain in the school. The military had earlier said most students and teachers had been evacuated.

Revenge

Khurrassani said the attack was revenge for the killing of hundreds of innocent tribesmen during repeated army operations in provinces including South Waziristan, North Waziristan and the Khyber Agency -- all restive regions along Pakistan's border with Afghanistan.

For the past few months, the Pakistan military has been conducting a ground offensive aimed at clearing out militants in these areas. The campaign has displaced tens of thousands of people.

READ: Pakistan offensive leaves 'ghost towns'

Northwestern Pakistan is home to loosely governed tribal areas. It's also a base for foreign fighters and a refuge for members of the Taliban and other militant groups.