The U.N. children’s fund warns that 220,000 children in the area of eastern Ukraine controlled by Russian-backed rebels are at risk of being killed or maimed by landmines and other explosive remnants of war.

Eastern Ukraine is one of the most mine-contaminated places on earth. Well into its fourth year of war, the Donetsk and Luhansk regions are riddled with deadly explosives that are taking a heavy toll on the lives and well-being of its children.

The U.N. children’s fund estimates landmines and other explosive weapons kill or maim one child a week along eastern Ukraine’s contact line. This is a 500-kilometer strip of land that divides government and rebel-controlled areas where fighting is most intense.

UNICEF warns children, especially very young children, are at great risk of death and injury from these lethal weapons. The agency says most casualties occur when children pick up these explosive devices, which look like toys.

During mine awareness demonstrations, educators teach children how to protect themselves from landmines, unexploded ordnance and other deadly remnants of war.

Since 2015, UNICEF and partners have reached more than half a million children in eastern Ukraine with this message through entertaining theatrical skits and interactive shows.

While these weapons pose an ever-present danger to children, UNICEF says they also can damage crucial infrastructure, such as water, electricity and gas facilities.

In one incident earlier this month, UNICEF says, unexploded ordnance was found at the Donetsk Filter Station, a facility that provides water to nearly 350,000 people in the region.