Two Nigerian military officers face court martial after an investigation into an army drone strike that killed 85 civilians  mistaken for militia gunmen, the army said on Thursday.

The military already acknowledged the drone accidently struck Tudun Biri village in northwest Kaduna state in December killing residents as they celebrated a Muslim festival in one of the country's worst airstrike errors.

"The military has conducted a painstaking investigation into the incident and has initiated disciplinary action against those culpable," the statement said. "Accordingly, the affected 2 personnel are to face a court martial for acts of omission or commission with respect to the incident."

The statement did not give further details about the two officials, their role in the accident or the proceedings.

Air strike accidents are not uncommon in Nigeria, where the military is fighting a jihadist conflict in the northeast and also heavily armed criminal gangs in the northwest, where they carry out mass kidnappings for ransom and raids on villages.

Nigerian forces often rely on air strikes against Islamist militants and bandit militias who operate in remote areas where state presence is weak and hide out in bases concealed deep in forests.

The military said troops were carrying out aerial patrols in December in Kaduna when they observed a group of people and "misinterpreted their pattern of activities to be similar to that of the bandits", before the drone strike was launched.

Calling the mistake "disturbing", President Bola Ahmed Tinubu ordered a probe,

The UN human rights office said it deplored the attack, noting that it was the latest of at least four airstrikes that have resulted in significant civilian fatalities since 2017.

It called on the government to take steps in future to ensure civilians and civilian infrastructure are protected and to review the rules of engagement and operating procedures.

The military said it was clearly an accident and offered  condolences to the families and relatives of those killed.

"It is hoped that there would be no repeat of strikes on non-combatants in ongoing operations," it said. "The military will take extra precautions in the future to ensure that non-combatants are safe."