Three children were killed and two others injured Wednesday when a grenade they found in a field exploded in northwest Pakistan, officials said.

The four brothers and a neighbour were playing when they found the rusty grenade near a village on the outskirts of the northwestern city of Peshawar.

“The children first played with it and later hit it with a stone causing it to explode,” Mansoor Aman, a local senior police official, told AFP.

Local police official Aziz ur Rehman confirmed the casualties.

Accidents involving discarded ordinance are not uncommon in Pakistan’s northwest.

Old mortar, artillery shells, and other discarded ammunitions are often smuggled into the country from Afghanistan, some dating back to the Soviet war in the 1980s.

The area was also once a hub of anti-Taliban activities, with locals forming militias to fight against the insurgents.

Last year, five people were killed when a worker at a scrap metal shop tried to recycle an old mortar shell that exploded as he tampered with it. (AFP)