Islamabad (PTI): At least 25 people were injured, some of them seriously, in a blast at a mosque in the northwestern Pakistani city of Dera Ismail Khan on Thursday, witnesses said.

Witnesses and local residents said a grenade was lobbed into the mosque while a large number of people were praying inside. 'Dera Ismail Khan has witnessed several bomb attacks in the past few months. The city is located near South Waziristan tribal region and Bannu and Tank districts of the North West Frontier Province, where the Pakistani Taliban have a strong presence.