A group of militants stormed Bacha Khan University in volatile northwestern Pakistan on Wednesday using the cover of thick fog, police said, with firing inside the campus still going on and eight explosions heard.

A professor of the Chemistry Department succumbed to his injuries after being rescued, rescue officer Mujahid Khan told Newsweek. Saeed Wazir, the deputy inspector general of police in Charsadda, told media two students had also been killed by the extremists. District Hospital officials, meanwhile confirmed they had already received 50 injured.

The militants entered the Bacha Khan University in Charsadda, northwestern Khyber Pakhtunkhwa province, early on Wednesday before opening fire on students and teachers in classrooms and hostels, two police officials said.

Vice Chancellor Fazal Rahim told reporters that several students were stuck inside the campus buildings.

The army and police had moved into the university and a gunfight with the attackers was under way, Deputy Inspector General Saeed Wazir told Reuters. He said it was unclear how many gunmen were involved.

Television images showed female students clutching hands as they fled the university, with traffic blocked on the roads of Charsadda as security forces rushed towards the campus. Hundreds of parents are lined up outside the university hoping for news of their children. There were scenes of panic as several parents were unable to reach anyone due to cellphones being off or otherwise inaccessible.

“We launched an operation inside the university and are trying to rescue the students and staff of the institution,” Wazir said.

Pakistan has killed and arrested hundreds of suspected militants under a counter-terrorism plan enacted after a massacre of school children in December 2014 in the northwest. Police said the gunmen had used the cover of a thick fog on a wintry morning to storm the campus.