WASHINGTON: The US military will leave behind about 800 square miles of land littered with undetonated grenades, rockets and mortar shells as it withdraws from Afghanistan by the end of this year, The Washington Post reported on Thursday.

According to this report, the explosives have already killed dozens of Afghan children who stumbled upon the ordnance at the poorly marked sites.

“Casualties are likely to increase sharply,” the report warned, adding that the US military has removed the munitions from only 3 per cent of the territory covered by its sprawling ranges. Clearing the rest of the contaminated land – twice as big as New York City – could take two to five years. US military officials say they intend to clean up the ranges but do not have the funds required to do so. The clean-up is expected to cost $250 million.

Since 2012, the UN Mine Coordination Centre of Afghanistan has recorded 70 casualties in and around US or Nato firing ranges or bases, and the pace of the incidents has been quickening. The Washington Post found 14 casualties not included in the UN data. Of the casualties recorded by the United Nations, 88pc were children.

A US official told the Post that the military shuttered more than half of its 880 bases in Afghanistan and withdrew the bulk of its troops before crafting a plan for removal of the unexploded ordnance. Some of the ranges that are peppered with explosives were closed as long ago as 2004. Now there are fewer service members to help conduct surveys.

US and Nato forces have used 240 high-explosives ranges in the 12-year-old war, some of which are the size of cities. The main range in the southern province of Helmand, for example, is 120 square miles, nearly twice the size of Washington.

US officials estimate that each range has thousands of undetonated explosives. Last year, contractors removed 32,000 pieces of ordnance in a 60-square-mile area — the only stretch cleared so far.