Militants have slaughtered at least 20 people and wounded dozens of others at a university in northwestern Pakistan on Wednesday, though there are conflicting reports whether the Taliban is claiming responsibility.
Reuters noted that government officials are warning the death toll at Bacha Khan University in the city of Charsadda could rise to 40, with Pakistan's army continuing to carry out operations in the campus and in the surrounding area in the search for suspects.
At least four of the armed gunmen are dead, officials said, though it is not clear if others were involved.
A senior Pakistani Taliban commander initially claimed responsibility for the assault, but an official spokesman for the group later denied involvement, describing the attack as "un-Islamic."
Mohammad Khurrassani, from the Pakistan Taliban's central organization, said the group "strongly condemn the attack on Bacha Khan University in Charsadda and disown the attack, saying this is not according to Shariah."
Pakistan continues to battle terrorism on its territory, especially in the regions closest to the border with Afghanistan.
"We've seen consistent operations by the Taliban up in this area," CNN counterterrorism analyst Phil Mudd said. "I see this as simply as retaliatory, that is the Taliban saying, 'If you're going to bring Pakistani special forces and the army up into our turf, you're going pay a heavy price.'"
The Pakistani branch of the Taliban carried out another mass school attack in December 2014, which left 132 children and nine staff members dead in the city of Peshawar. The group later attempted to justify the attack as revenge for the Pakistan's army's numerous operations against them, which they said had caused their families to suffer heavy losses as well.
Back then the attack was condemned by the Afghan branch of the Taliban, however, saying that the killing of children goes against the Islamic faith.
"The intentional killing of innocent people, children and women is against the basics of Islam and this criteria has to be considered by every Islamic party and government," spokesman Zabihullah Mujahid said.
Television footage of the latest attack apparently showed that many of the dead were shot in the head execution-style.
The gunmen are believed to have scaled the university walls on Wednesday morning, before entering different buildings and opening fire on students and teachers.
Witnesses to the attack said that the attackers chanted Islamic slogans as they carried out the shooting.
"We saw three terrorists shouting, 'God is great!' and rushing towards the stairs of our department," said one student, who wasn't named, according to BBC News.
"One student jumped out of the classroom through the window. We never saw him get up."
Reports are also emerging of a chemistry lecturer, named Syed Hamid Husain, who apparently shot at the gunmen to allow his students to flee, before he was shot dead.
"He was holding a pistol in his hand," Geology student Zahoor Ahmed told AFP news agency.
"Then I saw a bullet hit him. I saw two militants were firing. I ran inside and then managed to flee by jumping over the back wall."