Four children were killed when they played with a mortar in Afghanistan's northeastern Kunduz province, police said on April 11.
Seven other children were wounded, said police spokesman Mafuz Akbari. The explosion took place in Qasaban village of Chahardarah district on April 10. Chahardarah is a Taliban stronghold in Kunduz.
Decades of war in Afghanistan has left vast stretches of land dotted with mines, improvised explosive devices and unexploded munitions, say experts from the government's mine action coordination center.
In 2016, the United Nations documented "the highest number of civilian casualties caused by the detonation of explosive remnants of war since the mission began recording civilian casualties in 2009."
Most of the victims were children. Last year, 217 people were killed and 507 injured in such incidents, according to the UN report. That was an increase of 66 percent over 2015.