KABUL, Afghanistan – The U.S.-led coalition is failing to clear unexploded munitions from the Afghan bases it is demolishing as it withdraws its combat forces, leaving a deadly legacy that has killed and maimed a growing number of civilians, U.N. demining officials charge.

Grenades and shells left on the firing ranges where troops practiced with their weapons, and munitions fired at or from the bases that didn’t initially explode, have killed more than 50 civilians in nine provinces since 2008, nearly all of them in 2012 and this year, after the base closings began in earnest, said Mohammad Sediq Rashid, director of the Mine Action Coordination Centre of Afghanistan. His organization coordinates demining across Afghanistan and falls under the U.N.’s Mine Action Service Office.

And those are just the cases in which the U.N. has specific details about the location of the ordnance. Broadly, in 2012 there were 363 civilian casualties in Afghanistan — or about 30 per month — that were attributed primarily to unexploded ordnance, though in some cases also to mines, Rashid said. For the first half of this year, there have been 241 such casualties, an increase of about 10 per month, he said.

Abigail Hartley, the program manager for the U.N. mine office, said she firmly believes that the increase in casualties is because of the so-called “explosive remnants of war” left in and around the closed bases and ranges.

“The international military is supposed to be here protecting civilians and basically as a result of their presence, civilians are getting killed,” Hartley said.

The failure of the American-led International Security Assistance Force to undertake a proper cleanup is a violation of its obligations under the 1980 Convention on Certain Conventional Weapons, Hartley said.

ISAF has standard procedures in place to remove unexploded ordnance from firing ranges at its bases throughout Afghanistan, John Manley, an ISAF spokesman, wrote in an emailed statement Thursday in response to questions about left-behind ordnance.

“These procedures include mitigating ranges that are no longer in use,” he wrote. “Safety of civilians is one of our highest priorities.”

Hartley said her office has asked to see these standard procedures but hasn’t received them, and also has received no evidence of any cleanup.

Sarah Marshall, the deputy program manager of the U.N. mine office, said she and other officials have been meeting with ISAF officials for nearly two months trying to get more information on the closed bases and any cleanup efforts, but they have made little progress.

“And at a rate of 10 additional casualties a month, I’d say that two months is a long time,” she said.

In late 2011 there were about 800 U.S. and NATO facilities across Afghanistan, according to ISAF figures. More than 600 of them, mostly tiny bases used by a few dozen troops or less, already had been shut down or handed over to the Afghan government by the beginning of 2013, when the focus began shifting to larger bases.

Some of those closed had large, formal firing ranges with built-up berms, others had informal areas used for practice and sighting in weapons.

In many cases, those killed or injured around the bases are collecting scrap metal, grazing livestock or collecting firewood, Rashid said.

“As soon as a base is abandoned, it’s well known that people will rush towards it to find scrap metal to sell,” he said.