A deadly air strike on a Doctors Without Borders (MSF) hospital was "caused primarily by human error", the US commander in Afghanistan has said, promising disciplinary action as he detailed a US investigation into the catastrophic attack.

The October 3 air raid on the French charity's hospital during a Taliban offensive in the northern city of Kunduz killed at least 30 people, sparked an avalanche of global condemnation and forced the facility to close.

The "tragic but avoidable accident (was) caused primarily by human error," General John Campbell told reporters on Wednesday at NATO headquarters in Kabul, adding those most closely associated with the incident had been suspended from their duties.

He blamed in part the fatigue of US troops who had been battling a Taliban offensive in Kunduz for five days, adding that the mistake was "compounded by process and equipment failures".

The Special Operations AC-130 gunship aircraft hit the hospital instead of a nearby Afghan intelligence compound that was thought to have been commandeered by Taliban fighters during their brief capture of the northern provincial capital, he said.

"The medical facility was misidentified as a target by US personnel who believed they were striking a different building several hundred metres away where there were reports of combatants," Campbell said.

Those who requested and executed the strike "did not undertake appropriate measures to verify that the facility was a legitimate military target", he said.

Some of those involved in the attacks failed to follow the rules of engagement, Brigadier General Wilson Shoffner said at the same news conference.

MSF has called for an independent international investigation, saying the attack could be found a "war crime".

Despite repeated questioning on the matter, Shoffner refused to say if there would be an additional international independent investigation.

"We believe the investigation completed was full and impartial, and we stand by the findings and recommendations, and we support the process by which it was conducted," he said.

The strike began at 2:08 am local time, Campbell said, and at 2:20 am MSF phoned the US military to report they were under attack.

"It took the headquarters and the US special operations commander until 2:37 am to realise the fatal mistake. At that time, the AC-130 had already ceased firing. The strike lasted for approximately 29 minutes," he added.

Electronic systems on board the gunship had malfunctioned, he said, cutting off much of its communications, and the aircraft had diverted from its path believing it had been targeted by a missile, degrading the accuracy of "certain target systems".

This meant that when the crew entered the coordinates they were directed to an open field some 300 metres from the intended target.

"The investigating officer found that the air crew visually located the closest, largest building near the open field which we now know was the MSF trauma centre," Campbell said.

The hospital appeared similar to the description provided of the intended target, and at night the crew was "unable to identify any signs of the hospital's protected status".
"We have learned from this terrible incident," said Campbell.

"We will also take administrative and disciplinary action through a process that is fair and thorough (and) considers the available evidence."

Afghan President Ashraf Ghani welcomed the results of the investigation in a statement, saying the strike was a "painful demonstration of the cost of war".