"Relying only on an internal investigation by a party to the conflict would be wholly insufficient," a statement today from MSF General Director Christopher Stokes said.
"Not a single member of our staff reported any fighting inside the MSF hospital compound prior to the U.S. airstrike on Saturday morning. The hospital was full of MSF staff, patients and their caretakers," he said.
"We reiterate that the main hospital building, where medical personnel were caring for patients, was repeatedly and very precisely hit during each aerial raid, while the rest of the compound was left mostly untouched," the statement said. "We condemn this attack, which constitutes a grave violation of International Humanitarian Law."
U.S. Defense Secretary Ash Carter described the situation today as "confused and complicated."
Twenty two people were killed in Saturday's airstrike. Ten of those killed were patients, including three children, according to MSF. The other 12 were staff members, said MSF.
In a statement, the coalition in Afghanistan acknowledged that U.S. forces conducted an airstrike in Kunduz early Saturday at 2:15 a.m. local time "against insurgents who were directly firing upon U.S. service members advising and assisting Afghan Security Forces in the city of Kunduz. The strike was conducted in the vicinity of a Doctors Without Borders medical facility."
While Afghan officials have said there were Taliban fighters inside the hospital at the time, MSF said in response that it is "disgusted by the recent statements coming from some Afghanistan government authorities justifying the attack."
"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 said. "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.'"
The Associated Press contributed to this report.