At least seven students were killed and scores more wounded on Tuesday in a bomb attack on a Koran study class at a religious school in northwestern Pakistan, officials said.
More than 60 people had been taking a lesson when the explosion tore through the madrassa in Peshawar, about 170 kilometres (around 100 miles) west of Islamabad, said Waqar Azim, a senior police official.
"The blast took place in a seminary during a Koran class. Someone took a bag inside the seminary," Mr Azim told AFP.
He added that the person who had brought in the bag left the lecture hall before the blast.
Mohammad Ali Gandapur, another senior police official, said at least seven people had been killed with more than 50 wounded.
The death toll was confirmed by Mohammad Asim Khan, a spokesman at a local hospital, who told AFP that seven bodies and 70 wounded people had been taken to the facility.
"Most of those killed and injured were hit by the ball bearings and some were badly burnt," he said.
All of the dead were men aged between 20 and 40, he said. Teachers and boys as young as 7 were among the wounded.
No group claimed immediate responsibility for the attack.
The blast follows months of relative calm in Pakistan.
Peshawar was once the epicentre of militant violence in the country, with jihadists targeting security forces and public spaces in the city near the northwestern frontier with Afghanistan.
Violence in Pakistan has declined in recent years following a series of military operations along the border, but militant groups are still able to carry out deadly attacks.
In 2014, Pakistan's army launched a massive offensive to wipe out militant bases in the area and end the near decade-long insurgency that has cost thousands of lives.
The operation was intensified after the Pakistani Taliban killed more than 150 people, the majority of them children, at a school in Peshawar in December 2014.
Still, the Pakistani Taliban have been regrouping in recent months with several factions coming together in a pact, raising fears the jihadists may be regaining strength after launching a string of small-scale attacks on security forces along the border.