At least seven people have died after an explosion during a class at a religious school in Pakistan, police have said.

Children of various age groups are among the dead, an officer at the scene told the BBC.

Dozens of others were injured in the attack, which took place in the northern city of Peshawar.

No group has yet claimed responsibility. An investigation has been launched.

The city of Peshawar, close to the Afghan border, has seen some of the worst of the violence during the Taliban insurgency in recent years.

Six years ago, gunmen stormed a military school in the city leaving more than 150 dead, including many children.

What happened?

The blast took place at about 08:30 local time (03:30 GMT), police told the BBC.

About 60 people are understood to have been in the class at the religious school, known as a madrassa.

An eyewitness has told the police he saw a man enter the building with a bag of explosives shortly before the blast.

Police have confirmed to the BBC that a number of children are among the dead. Another officer told AFP news agency that two teachers were injured.

Hospital officials told Reuters news agency that they had received dozens of injured, many with burns.