At least 141 people were killed in an attack by Pakistani Taliban militants on a school in the northern Pakistani city of Peshawar, the AP news agency reported, citing Pakistani army spokesman Asim Baiva.

He said 132 children and nine other school workers were killed in the attack. At least 121 people were wounded. Doctors said many of those killed had been shot in the head and chest. Some were wounded by bombs dropped by the militants.

The Islamic militant organization Tehreek-e Taliban Pakistan claimed responsibility for the incident. Baiva stressed that there were seven attackers, all of whom were wearing suicide belts. Earlier, it was reported that nine criminals were killed.

Militant group spokesman Mohammad Khorasani earlier said the attackers were ordered to target only adult students and leave children alone.

Army spokesman Baiva later added that the gunmen had no intention of taking hostages and opened fire indiscriminately immediately after entering the school building.

The terrorists targeted the Army Public School, one of a network of 146 schools run by the military across the country that serve military and civilian children. There were about 500 students and teachers in the school building at the time of the attack.

The Pakistani army's operation to clear the school lasted several hours and ended on Tuesday afternoon.

Pakistani Prime Minister Nawaz Sharif told reporters that he believed the attack in Peshawar was a response to the military operation Zarb-e-Azb, which is being carried out against the Taliban in Waziristan.

Peshawar attack death toll exceeds 140