The attack in Charsadda began early on Wednesday, when militants entered the university campus by climbing over walls and shooting at a security guard.

Dozens were wounded and at least 20 people were killed in the raid, although a university security official said the death could reach as high as 40.

A Taliban leader, Khalifa Umar Mansoor, claimed responsibility for the attack, claiming that it was revenge for the militants killed by Pakistani security forces in recent months.

'Wipe out terrorism'

Pakistani Prime Minister Nawaz Sharif condemned the siege, saying the attackers had no faith or religion.

"We are determined and resolved in our commitment to wipe out the menace of terrorism from our homeland," Sharif said in a statement.

Among those killed on Wednesday was Chemistry lecturer Syed Hamid Husain, who has been hailed as a "martyr" by his students.

Witnesses of the attack said Husain attempted to protect his students by opening fire on Taliban militants after telling pupils to stay inside.

Twitter user Muneer Ahmed Kartio wrote: "Very #sad news Prof. Dr Syed Hamid from Chemistry dept embraced shahadat (martyrdom) in an attack in #BachKhanUniversity #Charsadda."

Teachers in northwestern Pakistan have been allowed to carry firearms in the classroom since the Taliban launched at attack at a school in nearby Peshawar in December 2014. More than 150 people, most of whom were children, were killed in the massacre, which was Pakistan's deadliest extremist attack to date.

Despite an increased military presence in western Pakistan, the beginning of 2016 has seen a wave of violence across the region. Wednesday's attack came just a day after a suicide bomber killed 10 people at a market on the outskirts of Peshawar.

ksb/sms (Reuters, AFP, AP, dpa)