MSF (Médecins Sans Frontières) demanded an immediate explanation on 3 October, after an airstrike hit a hospital run by the humanitarian organisation in the Afghan city of Kunduz. At least 19 people were killed in what the US military called possible "collateral damage" in the battle to oust Taliban insurgents.

MSF's Director of Operations in Brussels Bart Janssens said that while the hospital was not far from the conflict ongoing in Kunduz, the organisation did not believe there was any clear target close to the hospital. Almost 200 patients and employees were in the hospital, which is the only one in the region that can deal with major injuries, MSF said.

"We haven't had any communication yet from the international coalition, nor from the Afghan government directly to us. So that's why we clearly ask now, we want an explanation very fast and we want an independent investigation to be started," he said.

"We now know an aerial attack, of which carries very clearly the signature of being, a lot of indication, that it has been carried out by the international coalition forces in Afghanistan. What happened is that a plane arrived and in several ways it came four or five times over the hospital, and every time extremely precisely hit with a series of impacts on the main building of the hospital. This led to the horrible results of what we see," Janssens said.

MSF said it gave the location of the hospital to both Afghan and US forces several times in the past few months, most recently this week, to avoid being caught in a crossfire.

"The hospital is there since four years; it's a large hospital, the compound is larger than a football ground. And we have several times communicated through the GPS co-ordinates the exact location of the hospital to all warring parties in Afghanistan. So we really don't understand and we definitely do not accept the notification of collateral damage as we heard in the beginning in the first reaction," Janssens said.

MSF said it had treated almost 400 patients in the 150-bed hospital since fighting broke out during a Taliban insurgency, mostly for gunshot wounds. So many patients have flooded into the hospital they had to put in offices and on mattresses on the floor.

Bombing a 'tragic accident' – Obama

President Obama has announced that there will be an investigation into the attack. In a statement the US president said the "Department of Defense has launched a full investigation, and we will await the results of that inquiry before making a definitive judgment as to the circumstances of this tragedy".

The statement went on to say that Obama and First Lady Michelle Obama offered "thoughts and prayers to all of the civilians affected by this incident, their families, and loved ones", but that the US would continue to "work closely with President Ghani, the Afghan government, and our international partners to support the Afghan National Defense and Security forces as they work to secure their country".

Last week, a spokesman for Afghanistan's President Ashraf Ghani said there would be no airstrikes inside the city, because of the risk of mass civilian casualties. But yesterday, the Afghan government attempted to justify the bombing attack by claiming that Taliban fighters were in the hospital.

More about the Kunduz bombing