Islamabad, Pakistan - One university student has been killed and two others wounded during a violent mob attack after being accused of committing blasphemy in the northern Pakistani city of Mardan, police say.

The three men were attacked by fellow students while conversing in the cafeteria of the Abdul Wali Khan University on Thursday, local police official Pir Muhammad told Al Jazeera.

"Other students who overheard the victims talking first surrounded them and then started attacking them," said Muhammad.

"The two who were wounded have been taken to the hospital and are safe and sound."

According to local police official Tariq Aziz more than 100 people suspected of being part of the mob have been arrested so far.

In Pakistan, a shrine to murder for 'blasphemy'

Blasphemy against Islam is a sensitive subject in Pakistan, where punishment for the crime ranges from a fine to a mandatory death sentence, depending on the specific offence.

Currently, about 40 people are on death row or serving life sentences for blasphemy in Pakistan, according to the United States Commission on International Religious Freedom.

Increasingly, however, right-wing vigilantes and mobs have taken the law into their own hands, killing at least 69 people over alleged blasphemy since 1990, according to an Al Jazeera tally.

Those killed have included people accused of blasphemy, their lawyers, their relatives, judges hearing their cases and members of their communities.

Several people were arrested following the attack in Mardan on Thursday, and an investigation into who was responsible for instigating the violence was ongoing, said Muhammad.

Asad Hashim is Al Jazeera's Web Correspondent in Pakistan. He tweets @AsadHashim