The children were playing near a pond in the garrison town of Kohat with what officials describe as a “shell” apparently from a mortar.

Senior government official Khalid Khan Umarzai says Wednesday’s blast appeared to be an accident.

Islamist and criminal gangs are active in the Kohat region, and all sorts of weapons, including land mines and grenades, can be found in the area.

Kohat also lies near the tribal regions bordering Afghanistan, where Al-Qaeda and Taleban fighters have bases.