Medecins Sans Frontieres (MSF) has demanded an independent international investigation into air strikes that hit a hospital in Kunduz, Afghanistan, killing 22 people. Its director described the sustained attack on the facility as a "war crime".

"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," MSF general director Christopher Stokes said in a statement.

Earlier the same day, 4 October, US President Barack Obama said the US military would conduct an internal investigation into the incident. It will be carried out by the US Department of Defense. Nato said it has directed a multinational investigation and expected to deliver a report in the coming days.

"Relying only on an internal investigation by a party to the conflict would be wholly insufficient," Stokes' statement added.

Number of victims rises

On Sunday, 4 October, the death toll from the air strike on the hospital rose from 19 to 22.

Afghan officials have attempted to justify the attack by saying that Taliban fighters fired on Afghan troops from the hospital. Stokes strongly denied this.

"Not a single member of our staff reported any fighting inside the MSF hospital compound prior to the US airstrike on Saturday morning," he said in the statement. "The hospital was full of MSF staff, patients and their caretakers. It is 12 MSF staff members and 10 patients, including three children, who were killed in the attack."

Stokes said the main hospital building, which houses the accident and emergency and intensive care units was hit "repeatedly and very precisely hit during each aerial raid, while the rest of the compound was left mostly untouched".

He said that all critical patients had been referred to other health facilities, and MSF had pulled its staff out of the hospital.

In recent days, there has been fierce fighting in Kunduz, after Taliban fighters swept into the city last week.