An Afghan military air strike targeting the Taliban in northern Kunduz province is reported to have killed civilians.
Eyewitnesses said that helicopters targeted a gathering at a religious school in Dasht-e Archi district.
The government says at least 25 Islamists were killed or injured, but a doctor in Kunduz city told the BBC that more than 50 severely injured people were brought to his hospital.
The Taliban said no fighters were there and only civilians were killed.
The hospital doctor, who did not want to be named, said students and civilians were among the casualties. The district is controlled by the Taliban.
Local police told Reuters news agency that a representative from the Taliban leadership council, based in Quetta, in Pakistan, was visiting the area.
He said he was aware of civilian casualties but could not provide details. He said those targeted were Taliban fighters planning an operation, and that 15 were killed and 10 injured.
Some local reports said the strike hit a mosque, but it is unclear if the religious school was part of a mosque complex.
"When the planes came at around 12:00 some kids screamed 'they will drop a bomb' but the elders said 'calm down, nothing is going to happen', but then in an instant bombs hit the mosque," witness Mohammad Ishaq told AFP news agency.
He said those in the building were a mix of civilians, religious school students and Taliban fighters. He said they were attending a graduation ceremony.
A Taliban spokesman claimed that 150 civilians were killed or wounded in the attack.
US forces were not involved in any air strikes in Kunduz on Monday, a spokesman for US forces in Afghanistan said.
The number of air strikes carried out by Afghan and US forces has surged since a new strategy was announced by US President Donald Trump in August.
But the UN has noted an increase in civilian casualties as more air strikes have been carried out.
In 2017, the UN recorded 631 civilian casualties from air strikes by pro-government forces, including international military forces, a 7% increase from 2016 even though total civilian casualties decreased by 9%.
It was the highest number of civilian casualties from air strikes in a single year since the UN started systematic recording in 2009.