Volunteers carry a wounded student to hospital in Peshawar on December 16. Source: AP

A soldier takes position on a bunker close to the Army Public School under attack by Taliban gunmen on December 16. Source: AP

Troops arrive at the Army Public School on December 16. Source: AP

Parademics unload students from an ambulance on December 16. Source: AP

Parents arrive at Army Public School in Peshawar on December 16 after it was stormed by the Taliban. Source: AFP

A suicide bomber attacked the Army Public School in the northwestern city of Peshawar and gunmen went from classroom to classroom, shooting children.

The Tehreek-e-Taliban Pakistan claimed responsibility for the attack as retaliation for a military offensive in the region, saying militants had been ordered to shoot older students.

Indian Prime Minister Narendra Modi strongly condemned the “cowardly” attack, branding it “a senseless act of unspeakable brutality” and saying India shares rival Pakistan’s pain.

“Strongly condemn the cowardly terrorist attack at a school in Peshawar,” Mr Modi tweeted.

“It is a senseless act of unspeakable brutality that has claimed lives of the most innocent of human beings — young children in their school.”

The attack began about 10.30am (4.30pm AEDT) when a group of at least five insurgents, ­reportedly in military uniforms, entered the school.

Pakistan’s military headquarters said troops exchanged fire with the attackers for more than eight hours before the siege ended with the death of all six militants.

A security official said hundreds of students and staff were in the school when the ­attack began, although according to the military the bulk of them have been evacuated. It was not clear how many are still in the school.

Peshawar’s Lady Reading Hospital received 26 bodies, spokesman Jamil Shah said, while a report from the Combined Military Hospital said they had 69 dead. Provincial Information Minister Mushtaq Ghani said many of the dead were killed in the suicide blast.

Mudassar Abbas, a physics laboratory assistant at the school, said some students were celebrating at a party when the attack began. “I saw six or seven people walking class-to-class and opening fire on children,” he said.

A student said soldiers came to rescue the children during a lull in the firing.

“When we were coming out of the class, we saw dead bodies of our friends lying in the corridors. They were bleeding. Some were shot three times, some four times,” the student said. “The men entered the rooms one by one and started indiscriminate firing at the staff and ­students.”

Distraught parents thronged Lady Reading Hospital in the wake of the attack, weeping uncontrollably as children’s bodies arrived, their school uniforms drenched in blood.

Irshadah Bibi, 40, whose 12-year-old son was among the dead, beat her face in grief, throwing herself against an ambulance.

“O God, why did you snatch away my son? What is the sin of my child and all these children?” she wept.

The school on Warsak Road is part of the Army Public Schools and Colleges System, which runs 146 schools nationwide for the children of military personnel and civilians. Students are aged from 10 to 18. The schools educate the children of officers and non-­commissioned soldiers and army wives often teach in them.

TTP spokesman Muhammad Khorasani said there were six ­attackers. “They include target killers and suicide attackers. They have been ordered to shoot the older students but not the children,” he said.

“This attack is a response to Zarb-e-Azab and the killing of Taliban fighters and harassing their families.”

Zarb-e-Azb is the name for the army’s offensive against strongholds of the Taliban and other militants in North Waziristan.

The military has hailed the ­operation as a success in disrupting the TTP’s insurgency, which has killed thousands of Pakistanis since it erupted in 2007.

More than 1600 militants have been killed since the launch of Zarb-e-Azb in June, according to data compiled by Agence France-Presse from military statements.

Talat Masood, a retired ­general and security analyst, said the ­attack was intended to weaken the military’s resolve. “It is both tactical and strategic. The militants know they won’t be able to strike at the heart of the military, they don’t have the ­capacity because the army are prepared,” General Masood said. “So they are going for soft ­targets. These attacks have a great psychological impact.”

The semi-autonomous tribal areas that border Afghanistan have for years been a hideout for Islamist militants of all stripes — including al-Qa’ida and the home-grown TTP as well as foreign fighters such as Uzbeks and Uighurs.

Washington pressed Islamabad for years to wipe out the sanctuaries in North Waziristan, which militants have used to launch ­attacks on NATO forces in ­Afghanistan.

AFP