Doctors Without Borders says it is under “the clear presumption that a war crime has been committed” after a U.S.-led NATO coalition bombed its hospital in Kunduz, Afghanistan.

The aid organization, referred to internationally in French as Medecins Sans FrontiÃ¨res (MSF), asserted that it “condemn[s] this attack, which constitutes a grave violation of International Humanitarian Law.”

The U.S. military’s version of the story behind the bombing is full of holes, and constantly changing. After launching airstrikes on Kunduz, which has recently seen an insurgency by the Taliban, on Saturday morning, NATO said its bombing “may have resulted in collateral damage to a nearby medical facility.”

At least 23 people people were killed in the airstrikes, including 13 staff members and 10 patients, three of whom were children. A minimum of 37 more were wounded. A hospital nurse said there “are no words for how terrible it was,” noting “patients were burning in their beds.”

Uncertainty dominated Washington’s earliest account of the attack. The media echoed this ambiguity, but MSF insisted all “indications currently point to the bombing being carried out by international Coalition forces” led by the U.S. The humanitarian organization stressed that it had “communicated the precise locations of its facilities to all parties on multiple occasions over the past months” and yet, despite this, the NATO bombing of the hospital continued for over 30 minutes, even after MSF “frantically phoned” Washington.

Subsequently, the U.S. and Afghan governments moved away from describing the attack as an accident, a tragic instance of “collateral damage,” and proceeded to imply the bombing was intentional. Afghan officials claimed the hospital was being used as a “base” for the Taliban. “The hospital has a vast garden, and the Taliban were there,” insisted Kunduz acting Governor Hamdullah Danishi.

MSF was not buying it. The aid organization called the “Taliban base” claims “spurious” and said it is “disgusted by the recent statements coming from some Afghanistan government authorities justifying the attack.”

The organization flatly denied that the Taliban was ever fighting from its hospital. “Not a single member of our staff reported any fighting inside the MSF hospital compound prior to the U.S. airstrike,” MSF recalled.

“These statements imply that Afghan and US forces working together decided to raze to the ground a fully functioning hospital with more than 180 staff and patients inside because they claim that members of the Taliban were present,” MSF stated. “This amounts to an admission of a war crime. This utterly contradicts the initial attempts of the US government to minimize the attack as ‘collateral damage.'”