Doctors Without Borders (MSF) delivered a petition signed by 547,000 people to the White House Wednesday demanding an independent investigation into a deadly US strike on one of its hospitals in Afghanistan.
The October 3 bombing of the hospital in the northern city of Kunduz killed 30 people and forced the charity to close the trauma center -- the only one in the region -- while sparking global condemnation.
General John Campbell, the US commander in Afghanistan, said late last month the strike was "caused primarily by human error," but refused to say if there would be an independent investigation.
Adding to growing pressure, the MSF petition urged President Barack Obama to agree to a probe by the International Humanitarian Fact-Finding Commission (IHFFC).
The IHFFC is an independent body created under international law, but has never been used.
"Only a full accounting by an independent, international body can restore our confidence in the commitments of the United States to uphold the laws of war, which prohibit such attacks on hospitals in the strongest terms," Jason Cone, executive director of MSF-USA, said in a statement.
"It is not sufficient for the perpetrators of attacks on medical facilities to be the only investigators."
MSF has slammed American forces for "gross negligence" over the hospital strike, which also triggered calls for an independent investigation from Human Rights Watch.
A non-binding resolution passed in the European Parliament also urged an "independent investigation" into the hit.