The Pakistani Taliban fighters (TTP) says it carried out the attack on the military-run school in Peshawar in Pakistan's northwest in-response to the army's operation against it in the North Waziristan tribal area.

Pakistani Prime Minister Nawaz Sharif said it was a "national tragedy", calling those killed "my children".

Muhammad Khorasani, TTP spokesperson, told Al Jazeera the suicide bombers had been given orders to allow the youngest students to leave but to kill the rest.

Al Jazeera's Osama Javaid reports from Peshawar.