KUNDUZ: The head of an international medical charity whose hospital in northern Afghanistan was destroyed in a US airstrike says the "extensive, quite precise destruction" of the bombing raid casts doubt on American military assertions that it was a mistake.

The Oct. 3 attack on the compound in Kunduz city, which killed at least 22 patients and hospital staff, should be investigated as a possible war crime, said Christopher Stokes, general director of Doctors Without Borders, which is also known by its French abbreviation MSF.

The trauma hospital was bombed during a firefight between Taliban and government troops, as US advisers were helping Afghan forces retake the city after the insurgents overran it and seized control on Sept. 28. Afghan authorities say they are now largely back in control of Kunduz.

US President Barack Obama has apologized for the attack, and the commander of US and NATO troops in Afghanistan, Gen. John F. Campbell, said it was a mistake. He said the strike had been called in by Afghan forces, but has not explained exactly how it happened or who granted final approval. Internal military investigations are underway, with preliminary results expected in coming days.

According to Associated Press reporting, American special operations analysts were scrutinizing the Afghan hospital days before it was destroyed because they believed it was being used by a Pakistani operative to coordinate Taliban activity. The analysts knew it was a medical facility, according to a former intelligence official who is familiar with some of the documents describing the site.

It's unclear whether that information ever got to commanders who unleashed the AC-130 gunship on the hospital.

"The hospital was repeatedly hit both at the front and the rear and extensively destroyed and damaged, even though we have provided all the coordinates and all the right information to all the parties in the conflict," Stokes said, standing in the burned-out main hospital building.

"The extensive, quite precise destruction of this hospital ... doesn't indicate a mistake. The hospital was repeatedly hit," Stokes said. The bombing went on for more than an hour, despite calls to Afghan, US and NATO to call if off, MSF has said.

Stokes, who has called for an independent inquiry into the incident, told The Associated Press in an interview in the remains of the hospital on Friday that MSF wanted a "clear explanation because all indications point to a grave breach of international humanitarian law, and therefore a war crime."

Afghan authorities have refused to comment before investigations are complete. President Ashraf Ghani's deputy spokesman, Zafar Hashemi, told reporters on Saturday that the Afghan government has "faith" in investigations being conducted by the US military, and by a joint Afghan-NATO team.

MSF has denied there were any armed Taliban on the hospital grounds at the time of the attack. "The compound was not entered by Taliban soldiers with weapons," Stokes said. "What we have understood from our staff and guards is that there was very strong, very good control of what was happening in and around the compound and they reported no firing in the hours preceding the destruction of the hospital."

More than 70 staff members were on duty, tending to more than 100 patients at the time, he said.

According to its policy, MSF treats government troops and insurgent combatants equally. Hospitals are regarded as protected sites in war.

Doctors Without Borders officials have said the US gunship made five separate strafing runs over the course of an hour, directing heavy fire on the main hospital building, which contained the emergency room and intensive care unit. Surrounding buildings were not hit. The hospital is no longer operable.

Stokes said that "until we understand what happened and we can gain guarantees that this unacceptable attack cannot happen again, we cannot reopen and put our staff in danger."

MSF, a Nobel Peace Prize-winning organization that provides medical aid in conflict zones, has called for an investigation by the International Humanitarian Fact-Finding Commission, based in the Swiss capital, Bern. It is made up of diplomats, legal experts, doctors and some former military officials from nine European countries, including Britain and Russia.

An IHFFC investigation needs the cooperation of both Afghanistan and the US before it can proceed, which neither government is expected to give.