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Doctors Without Borders called for an unprecedented international and independent humanitarian fact-finding commission on Wednesday into the deadly U.S. bombing of its hospital in northern Afghanistan.

The U.S. military has pledged a full investigation and admitted the airstrike on the Kunduz hospital — which killed 22 people — was a mistake.

Doctors Without Borders — also known as Medecins Sans Frontieres, or MSF — has called the airstrike a war crime.

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The organization on Wednesday called for a probe from the little-known International Humanitarian Fact Finding Commission, saying that international humanitarian law isn't about "mistakes" but "intentions, facts and rights."

"This was not just an attack on our hospital, it was an attack on the Geneva conventions," said Joanne Liu, president MSF International. "This cannot be tolerated."

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MSF’s hospital in Kunduz was the only facility of its kind in northeastern Afghanistan, and the charity said its destruction has left thousands without access to care.

The U.S., NATO and Afghan forces will be conducting separate investigations — but Liu said that MSF wants the separate fact-finding mission to independently examine potential breaches of international humanitarian law.

"Today, we are fighting back for the respect of the Geneva conventions," she said. "If we let this go, we are basically giving a blank check to any countries who are at war."

The International Humanitarian Fact Finding Commission was established in 1991 as "a permanent international body whose main purpose is to investigate allegations of grave breaches and serious violations of international humanitarian law."

MSF said it is awaiting responses to letters it sent Tuesday to 76 countries that have signed Article 90 of the additional protocol to the Geneva Conventions, seeking to mobilize the commission. In this case, the United States and Afghanistan — which are not signatories — must also give their consent to such a mission. MSF says it has had no response yet from the United States or any other countries.

"Governments up to now have been too polite or afraid to set a precedent," Liu said. "The tool exists and it is time it is activated."