A group of militants stormed a university in volatile northwestern Pakistan on Wednesday, January 20, using the cover of thick fog, police said, with firing inside the campus still going on and two explosions heard. Media reported that a chemistry professor had been killed and 50 people wounded in the attack.

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 said. He said it was unclear how many gunmen were involved.

Television footage showed soldiers entering the campus as ambulances lined up outside the main gate and anxious parents consoled each other. “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.

The Bacha Khan University teaches over 3,000 students and hosted an additional 600 visitors on Wednesday for a poetry recital, the vice chancellor said. Shabir Khan, a lecturer in the English department, said he was about to leave the hostel for the department when firing began.

“Most of the students and staff were in classes when the firing began,” Khan said. “I have no idea about what’s going on but I heard one security official talking on the phone to someone and said many people had been killed and injured.”