An air strike on a hospital in the Afghan city of Kunduz that killed at least 19 people is “utterly tragic, inexcusable, and possibly even criminal,” said the UN High Commissioner for Human Rights, calling for a transparent investigation.

READ MORE: 9 MSF staff, 7 patients killed after US airstrike hits hospital in Kunduz, Afghanistan

"This deeply shocking event should be promptly, thoroughly and independently investigated and the results should be made public," Zeid Ra'ad al-Hussein said in a statement on Saturday.

"The seriousness of the incident is underlined by the fact that, if established as deliberate in a court of law, an airstrike on a hospital may amount to a war crime."

He described the bombing as "utterly tragic, inexcusable, and possibly even criminal."

"International and Afghan military planners have an obligation to respect and protect civilians at all times, and medical facilities and personnel are the object of a special protection. These obligations apply no matter whose air force is involved, and irrespective of the location."

The Kunduz attack constitutes a grave violation of International Humanitarian Law.We demand a full & transparent account from the Coalition — MSF International (@MSF) October 3, 2015

UN Secretary-General Ban Ki-moon strongly condemned the airstrikes and called for a thorough and impartial investigation into the attack in order to ensure accountability.

“The Secretary-General recalls that hospitals and medical personnel are explicitly protected under international humanitarian law,” the statement attributed to Ban said.He commended the courageous and dedicated staff of the organization and extended his deepest sympathies to the families of the victims.

Medecins Sans Frontieres (MSF) condemned “in the strongest possible terms” the bombing of its hospital full of staff and patients in a statement on Saturday.

“The bombing in Kunduz continued for more than 30 minutes after American and Afghan military officials in Kabul and Washington were first informed by MSF that its hospital was struck. MSF urgently seeks clarity on exactly what took place and how this terrible event could have happened,” it said.

#Kunduz Deeply outraged- All indications currently point bombing being carried out by international Coalition forces — Dr Joanne Liu (@JoanneLiu_MSF) October 3, 2015

They added that the precise locations of its facilities had been communicated to all parties in the military conflict on multiple occasions, with the latest communication being on September 29.

The MSF said that “all indications” point to the bombing having been carried out by US-led forces and demanded a “full and transparent account from the coalition” regarding its aerial bombing activities over Kunduz on Saturday morning.

“This attack is abhorrent and a grave violation of international humanitarian law,” said Meinie Nicolai, MSF President on Saurday. “We demand total transparency from coalition forces. We cannot accept that this horrific loss of life will simply be dismissed as ‘collateral damage’.”

“Besides resulting in the deaths of our colleagues and patients, this attack has cut off access to urgent trauma care for the population in Kunduz at a time when its services are most needed,” said Nicolai.

Appalled at loss of life & injuries to heroic @MSF medical staff and their patients in #Kunduz#Afghanistan air strike. Solidarity @UNOCHA — Kieran Dwyer (@KieranADwyer) October 3, 2015

MSF said in a statement that the hospital was bombed by a series of aerial raids at approximately 15 minute intervals. The bombs “very precisely” and “repeatedly” hit the main central hospital building, housing the intensive care unit, emergency rooms, and physiotherapy ward, it added.

“The bombs hit and then we heard the plane circle round,” said Heman Nagarathnam, MSF’s head of programs in northern Afghanistan.“There was a pause, and then more bombs hit. This happened again and again. When I made it out from the office, the main hospital building was engulfed in flames.

“Those people that could had moved quickly to the building’s two bunkers to seek safety. But patients who were unable to escape burned to death as they lay in their beds.”

WHO calls on all govts & military officers to observe their obligations under intl law, ensure protection of health serv in conflict #Kunduz — WHO (@WHO) October 3, 2015

Tragic news. @MSF please accept our condolences for the killing of your colleagues & patients in #Kunduz. https://t.co/M5gD9G139T — Yves Daccord (@YDaccordICRC) October 3, 2015

The International Committee of the Red Cross (ICRC) strongly condemned the violence against patients, medical workers and facilities, saying it was “deeply shocked,” in a statement on Saturday.

"This is an appalling tragedy. Such attacks against health workers and facilities undermine the capacity of humanitarian organizations to assist the Afghan people at a time when they most urgently need it," said Jean-Nicolas Marti, head of the ICRC delegation in Afghanistan. "Neutral and impartial humanitarian assistance is crucial today in Afghanistan," he added.

The ICRC called on all parties to ensure the safety of the civilian population, medical staff and facilities.

Human rights group Amnesty International characterized the Kunduz bobming as “a deplorable loss of life” and called for an urgent and impartial investigation.

“This bombing of the MSF hospital in Kunduz marks a dark day for humanitarianism. It is sickening to think that doctors and other staff have had to pay with their lives while trying to save others. Hospitals are places of sanctity under international law governing conflict,” said Horia Mosadiq, Afghanistan Researcher at Amnesty International. “We call on all parties to the conflict to respect and protect humanitarian personnel and facilities and take every precaution to protect civilians caught up in the conflict.”

Human Rights Watch has raised “grave concerns” about whether US forces took “sufficient precautions” to identify and avoid striking the facility.

“The bombing of the hospital is a shocking development for Kunduz, where civilians and aid workers are already at grave risk from the fighting,” said Patricia Gossman, senior Afghanistan researcher at Human Rights Watch. “All forces are obligated to do their utmost to avoid causing civilian harm.”

The failure of US forces to stop an attack from striking a hospital strongly suggests the forces may have violated the laws of war, the statement on the group’s website said. The organization urged for an open investigation and called on the US to review its targeting procedures to ensure such incidents do not reoccur.

LISTEN MORE:

NATO’s Secretary General has expressed his condolences to all those affected by the bombing of the hospital in Kunduz.

“I am deeply saddened by the tragic incident involving a Doctors without Borders hospital in Kunduz,” Jens Stoltenberg said in a statement on Saturday. “I extend my condolences to all those affected. A US investigation into this tragic incident is underway in coordination with the Afghan government.”

A hospital in the Afghan city of Kunduz has been hit and partially destroyed in an “aerial attack” that killed at least 19 people in the early hours of Saturday. Among the victims were 12 Medecins Sans Frontieres staff and seven patients, including three children.

NATO coalition spokesman Colonel Brian Tribus said US forces conducted an airstrike in Kunduz at 2:15am on Saturday. He admitted the strike might have “resulted in collateral damage to a nearby medical facility.”

The head of US-led forces in Afghanistan, General John Campbell, has offered condolences to Afghan President Mohammad Ashraf Ghani, Reuters reported citing the Afghan president’s office.

The US military said in a statement on Saturday that its air forces conducted a strike “in the vicinity” of a Medecins Sans Frontieres hospital in Kunduz.

US Defense Secretary Ash Carter said on Saturday that Washington had launched an investigation in coordination with the Afghan government. The area around the hospital has been the scene of intense fighting between US-Afghan troops and Taliban fighters in recent days, he added.

‘No words for how terrible it was’ – MSF nurse

MSF nurse Lajos Zoltan Jecs who had been inside the MSF facility during the bombing described the attack as “absolutely terrifying.”

“At first there was confusion, and dust settling. As we were trying to work out what was happening, there was more bombing,” he said, as cited by the MSF website.

“After 20 or 30 minutes, I heard someone calling my name. It was one of the Emergency Room nurses. He staggered in with massive trauma to his arm. He was covered in blood, with wounds all over his body. At that point my brain just couldn't understand what was happening. For a second I was just stood still, shocked.”

.@MSF nurse in Kunduz rescuing patients/staff: "There are no words for how terrible it was. In ICU 6 patients were burning in their beds." — Jason Cone (@jtcone1977) October 3, 2015

He recalls that the bombing lasted for about 30 minutes. After the airstrikes stopped he went to look for survivors.

“We tried to take a look into one of the burning buildings. I cannot describe what was inside. There are no words for how terrible it was. In the Intensive Care Unit six patients were burning in their beds,” he said.

The staff hid in a safe place, leaving a patient in the operating room on the table “dead, in the middle of the destruction,” he said.

“The first moments were just chaos. Enough staff had survived, so we could help all the wounded with treatable wounds. But there were too many that we couldn't help.”

He said that urgent surgery was carried out for one of the doctors on the office table but he did not survive.

“Some of my colleagues were in too much shock, crying and crying. I tried to encourage some of the staff to help, to give them something to concentrate on, to take their minds off the horror. But some were just too shocked to do anything.”

“What is in my heart since this morning is that this is completely unacceptable. How can this happen? What is the benefit of this? Destroying a hospital and so many lives, for nothing. I cannot find words for this.”