"The hospital was full of MSF staff, patients and their care-takers. It is 12 MSF staff members and 10 patients, including three children, who were killed in the attack," the statement said.
The air raid struck the hospital early Saturday. The US forces in Afghanistan which support Afghan forces in the war on Taliban militants and terrorists, said an investigation has been initiated into the case, Xinhua news agency reported.
"Under the clear presumption that a war crime has been committed, MSF demands that a full and transparent investigation into the event be conducted by an independent international body. Relying only on an internal investigation by a party to the conflict would be wholly insufficient," the statement said.
Following the air strikes, the aid agency has stopped functioning and evacuated all its international staff.
In a surprise attack, Taliban militants captured major parts of Kunduz city last Monday. Government forces have launched a counter-offensive and so far, according to Kunduz police, hundreds of Taliban militants have been killed.