At least 85 civilians were killed in Kaduna state, north-west Nigeria, in an air strike during a Muslim religious celebration on Sunday, the local emergency management authority said.
The civilians were "mistakenly killed" by a military drone "targeting terrorists and bandits", according to state Governor Uba Sani, who did not give a death toll.
The defence ministry termed the operation as "needless tragedy".
Dozens were wounded during the attack.
A state official, Samuel Aruwa, said an army officer "Maj VU Okoro, explained that the Nigerian army was on a routine mission against terrorists but inadvertently affected members of the community".
Defence spokesman Maj Gen Edward Buba in a statement on Tuesday said the airstrike was based on credible intelligence about the presence of "terrorists" in the area.
Governor Sani has ordered an investigation into the "tragic incident" that happened when villagers from Tundun Biri gathered for a religious festival on Sunday evening.
"The Northwest Zonal Office has received details from the local authorities that 85 dead bodies have so far been buried while search is still ongoing," a statement from the National Emergency Management Agency in the federal capital, Abuja, said.
"It is worthy of note that the casualties ranged from children, women and the elderly."
One man, who witnessed what happened, told the BBC, that there were two attacks.
"The aircraft dropped a bomb at the venue, it destroyed and killed our people including women and children," he said.
"The second bomb was dropped on some of us who went to bring dead bodies of the victims of the first blast. We lost about 34 people in my family and we have 66 injured people in the hospital."
A woman who saw the aftermath of the bombing told the BBC that bodies were strewn all over the place.
"Some women died holding their babies, some of the babies survived while others died along with their mothers," she said.
The Nigerian military has in the past been accused of causing civilian casualties while battling militia gangs, known locally as bandits, in the north-west of the country. The government has labelled the gangs "terrorists".
In 2021, at least 20 fishermen were killed accidentally in a Nigerian fighter jet strike on a jihadist camp in north-east Nigeria.
Over 300 people have been killed since 2017 in accidental strikes by the Nigerian forces, a report by SB Morgen, a research firm, said.
BBC