Medecins Sans Frontieres (MSF) said on Wednesday that an international humanitarian commission has been formally asked to investigate the U.S. bombing of its hospital in Kunduz, Afghanistan, that killed 22 people including 12 of its staff.

The medical charity had been demanding that the independent humanitarian commission created under the Geneva Conventions in 1991 be activated for the first time to handle the inquiry into the Oct. 3 airstrike.

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MSF has said the commission's inquiry would gather facts and evidence from the United States, NATO and Afghanistan, as well as testimony from MSF staff and patients who survived the attack. The partial destruction of its trauma hospital has left tens of thousands of Afghans without access to health care.

"We have received apologies and condolences, but this is not enough. We are still in the dark about why a well-known hospital full of patients and medical staff was repeatedly bombarded for more than an hour," said Dr. Joanne Liu, MSF International President. "We need to understand what happened and why."

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The fact-finding commission, composed of 15 experts, was established in 1991 under the Geneva Conventions that aims to protect civilians and non-combatants during war, but it has never been activated. 

MSF has previously said it was in talks with Swiss authorities to activate the commission. Swiss foreign ministry officials could not immediately be reached for comment.