Médecins Sans Frontières has demanded an independent inquiry into the US attack on a hospital in Kunduz, in which 22 people, inlcuding its staff, lost their lives.
The aid group said it was making the call for an inquiry "under the clear presumption that a war crime has been committed".
MSF tweeted: "The hospital was repeatedly and precisely hit during each aerial raid, while the rest of the compound was left mostly untouched.
"Not a single member of our staff reported any fighting inside the hospital compound prior to the US air strike on Saturday morning."
The US military said the results of a multinational preliminary investigation would be available "within days".
"Additionally, the US military has opened a formal investigation... to conduct a thorough and comprehensive inquiry," it added.