The death toll from Wednesday's Taliban attack on Bacha Khan University in Charsadda, northwestern Pakistan, rose to 21 Thursday after another student died in hospital, a police official told AP.
Four Taliban attackers were among the dead, as well as a chemistry professor who was hailed as a hero for shooting back at the attackers and allowing some students to escape, according to AP. Twenty-two students were injured, and Pakistan is holding a day of mourning in memory of the dead on Thursday.
The attack occurred during a local celebration at university, about 20 miles from the city of Peshawar, AP reported.
The Pakistani Taliban claimed responsibility for the attack in a phone call made to AP. A group leader, Khalifa Umar Mansoor, said a four-man team conducted the assault at the campus in the town of Chasadda. He says it was in revenge for the scores of militants the Pakistani security forces have killed in recent months.
However, another spokesman, Mohammad Khurasani, said Wednesday's attack was "un-Islamic" and insisted the Pakistani Taliban were not behind it. Such statements from among the Taliban are not uncommon since the group has many loosely linked factions.
TV stations in Pakistan broadcast footage showing a heavy military presence at the university campus. Ambulances were at the scene, taking the wounded to hospital.
Asim Bajwa, the director-general of the Inter-Services Public Relations (ISPR), the media wing of the Pakistan Armed Forces, said four terrorists had been killed in the attack. He said army troops were clearing the university building "block by block."
Imran Khan, the leader of the PTI party that rules the area where the university is located, condemned the attack, Geo TV reported.
"I am going to Charsadda myself, and will review the situation myself. We are united against terrorism and all of Pakistan is on [the same] page."
Prime Minister Muhammad Nawaz Sharif released a statement following the attack and said he was "deeply grieved."
"We are determined and resolved in our commitment to wipe out the menace of terrorism from our homeland. The countless sacrifices made by our countrymen will not go in vain Inshallah," Sharif said.
No one has yet claimed responsibility for the attack. In December 2014, more than 150 people, mostly children, were killed on a Taliban attack on a school in the area.
American Ambassador to Pakistan David Hale has also released a statement condemming the attack.
"The blatant disregard for human life displayed by these attackers is intolerable. It is especially reprehensible that the attackers targeted an educational institution where students and educators are seeking to better themselves and the nation of Pakistan. This attack stands in stark opposition to the desires of the Pakistani people to create a secure, stable, and prosperous country, based on respect for all. We offer our deepest condolences to the victims and their families during this time of grief.
"The United States stands with the government and people of Pakistan and is committed to supporting their efforts to fight terrorism. We support Pakistan's efforts to bring to justice those behind the attack."
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