A senior Pakistani Taliban commander claimed responsibility for the assault in Khyber-Pakhtunkhwa province, but an official spokesman later denied involvement, calling the attack “un-Islamic.”

The violence nevertheless shows militants retain the ability to launch attacks, despite a nationwide anti-terrorism crackdown and a military campaign against their strongholds along the lawless border with Afghanistan.

A security official said the death toll could rise to 40 at Bacha Khan University in Charsadda. The Army said it had concluded operations to clear the campus six hours after the attack began, and that four gunmen were dead.

A spokesman for rescue workers, Bilal Ahmad Faizi, said 19 bodies had been recovered, including those of students, guards, policemen and at least one teacher, named by the media as chemistry professor Syed Hamid Husain. Husain reportedly shot back at the gunmen with a pistol to allow his students to flee.