PESHAWAR • At least seven adult students were killed and scores more wounded yesterday in a bomb attack on a Quran study class at a religious school in north-western Pakistan, officials said.

Over 60 people were at a lesson when the explosion tore through the madrasah in Peshawar, about 170km west of Islamabad, senior police official Waqar Azim said.

"The blast took place in a seminary during a Quran class. Someone took a bag inside the seminary," Mr Azim said, adding that the person left the lecture hall before the blast at the Jamia Zuberia seminary.

The death toll was confirmed by local hospital spokesman Mohammad Asim Khan, who said seven bodies and 70 wounded people were taken to the medical facility.

"Most of those killed and injured were hit by ball bearings and some were badly burnt," he said, adding that all of the dead were men aged between 20 and 40.

Teachers and boys as young as seven were among the wounded.

"The blast took place in the section where students above the age of 18 were taking a class," teacher Safiullah Khan said.

The wall in the school that separated older students from the children collapsed, he added.

A live stream of the lesson showed a teacher speaking in Pashto and Arabic, explaining a saying from Prophet Muhammad, when the explosion took place.

In a tweet, Prime Minister Imran Khan offered his condolences: "I want to assure my nation we will ensure the terrorists responsible for this cowardly barbaric attack are brought to justice asap."

It was not immediately known why the school was targeted. No group has claimed responsibility.

Peshawar was once the epicentre of militant violence in Pakistan, with security forces and public spaces in the city targeted.

AGENCE FRANCE-PRESSE