Media playback is unsupported on your device Media caption Mashal Khan was killed by a mob of fellow students on campus

Pakistan's Prime Minister Nawaz Sharif has said he is "shocked and saddened" by the killing of a university student accused of blasphemy against Islam.

He says the state will not "tolerate" that citizens take the law "in their own hands".

The journalism student was brutally killed by fellow students on campus. Eight have now been charged with murder and terrorism, officials say.

Blasphemy is a highly sensitive and incendiary issue in Pakistan.

Critics say blasphemy laws, which allow the death penalty in some cases, are often misused to oppress minorities.

The murdered student has been identified as Mashal Khan, who was accused of posting blasphemous messages on social media.

Local media report he was stripped and beaten in the hostel at Abdul Wali Khan University in the northern city of Mardan.

Graphic video posted online showed dozens of men outside the building kicking and throwing objects, including planks, at a half-naked body sprawled on the ground.

Image copyright EPA Image caption A Pakistani official shows where a mob lynched the student's body

Mr Sharif, who has supported a wide-ranging crackdown on blasphemous content on social media, condemned the attack, in his first statement on Thursday's killing.

"The nation should stand united to condemn this crime and to promote tolerance and rule of law in society," he said.

"Let it be known to the perpetrators of this act that the state shall not tolerate citizens taking the law in their own hands."

The police have denied allegations that officers did not act to save Mr Khan's life, saying that the student was already dead when they arrived at the scene.

They have arrested 12 people over the incident and are hunting for more suspects.

Human rights activists held small protests in several Pakistani cities on Saturday condemning the murder, and the UN in Pakistan urged authorities "to take firm action and bring the perpetrators to speedy justice".

Image copyright EPA Image caption The student's room had posters of Karl Marx and Che Guevara and scribbled quotes including "Be curious, crazy and mad"

Witnesses told media that Mr Khan was disliked by other students for his liberal and secular views, and had been in a heated debate during a class the day he was killed.

The imam at the local mosque refused to lead the prayer at Mr Khan's funeral on Friday.

But the student's father said the accusations of blasphemy were unfounded. "First they killed my son and now they are adding salt to our wounds," Iqbal Shaer told Reuters news agency.

At least 65 people have been murdered in Pakistan after being accused of blasphemy since 1990, a recent think tank report said.