Medical aid group Medecins Sans Frontieres denied that Taliban fighters were firing from its hospital at Afghan and NATO forces before a U.S. air strike killed at least 19 people in a battle to oust the Islamist insurgents from an Afghan city.
The northern city of Kunduz has been the scene of fierce fighting since the Taliban captured it almost a week ago. Afghan security forces fought their way into Kunduz four days ago, but battles continue in many places.
The aid group has said an air strike, probably carried out by U.S.-led coalition forces, killed 19 staff and patients on Saturday in a hospital it runs in Kunduz, leaving 37 wounded.
The U.S. military said it conducted an air strike "in the vicinity" of the hospital, as it targeted Taliban insurgents who were directly firing on U.S. military personnel.
The U.S. government promised a full investigation into the incident as the U.N. human rights chief said the bombing could amount to a war crime.
In a statement, President Barack Obama offered condolences to the victims of what he called "the tragic incident".
In Kabul, the Afghan Ministry of Defense said Taliban fighters had attacked the hospital and were using the building "as a human shield". But the medical aid group denied this.
Afghan staff react inside a Medecins Sans Frontieres (MSF) hospital after an air strike in the city of Kunduz, Afghanistan in this October 3, 2015 MSF handout photo.
"The gates of the hospital compound were closed all night so no one that is not staff, a patient or a caretaker was inside the hospital when the bombing happened," Medecins Sans Frontieres said in a statement on Sunday.
Witnesses said patients were burned alive in the crowded hospital after the airstrike. Among the dead were three children being treated.
Frantic MSF staff telephoned military officials at NATO in Kabul and Washington after the attack, but bombs continued to rain down for nearly an hour, one official of the group said.
Taliban fighters in Kunduz were still holding out against Afghan troops, despite government claims to have taken control of the area.
The Afghan defense ministry on Sunday congratulated residents over the victory and military helicopters dropped 6,000 leaflets urging people to cooperate with the army.
"If you see abandoned military vehicles or equipment anywhere turn them over to security forces," the leaflets read.
A coalition military official in Kabul, who asked not to be named, said, "Our understanding is that the whole area is still contested."
Corpses lie in the streets and people are too afraid to leave their homes, said one resident, Gulboddin.
"You can hear the sound of gun fire all over the city," said Gulboddin, who has only one name. "Some of the bodies are decomposing."
Hospitals running out of medicine are struggling to treat growing numbers of patients, said public health official Sayed Mukhtar. "There is no electricity and hospital laboratories are not working," he added. "This city is no longer for living."