PESHAWAR, Pakistan (Reuters) – A bomb blast at a religious seminary in the Pakistani city of Peshawar on Tuesday killed at least seven people, including children, and wounded dozens, police and hospital officials said.

“Unknown people planted explosives in a plastic bag,” said a police officer in the northwestern city who declined to be identified as he is not authorised to speak to media.

Peshawar, near the border with Afghanistan, has long been plagued by Islamist violence.

Though the number of incidents in the city, and in Pakistan in general, had fallen over recent years, there has been an increase this year in attacks on the security forces in Khyber Pakhtunkhwa province, of which Peshawar is capital.

Some of the attacks have been claimed by the Pakistani Taliban.

A spokesman for the city’s Lady Reading Hospital said it had received seven dead and 70 wounded, many with burns.

Tariq Burki, the director of the hospital, said four of the dead were children.

The madrassa is largely for adult students and many were studying when the blast happened, said city resident Abdul Rahim, whose said his 27-year old cousin was among the wounded.

“He told us they were attending a class when the blast took place,” Rahim said.

Reuters