ABUJA, Nigeria (AP) — Two Nigerian military personnel will face a court martial over the killing of 85 villagers in a military drone attack in December in the West African nation’s conflict-battered north, authorities said, prompting calls from a rights group Friday for more transparency and justice for victims.

The two personnel will be subjected to military justice proceedings “for acts of omission or commission” after investigations found that the civilians killed by the strike “were mistaken for terrorists,” Nigeria’s Defense Headquarters spokesperson Maj. Gen. Edward Buba said in a statement Thursday without providing further details.

Nigeria’s military often conducts air raids as it fights the extremist violence and rebel attacks that have destabilized Nigeria’s northern region for more than a decade, often leaving civilian casualties in its wake.

Since 2017, some 400 civilians have been killed by such accidental strikes by the military, according to the Lagos-based SBM Intelligence security firm.

The December misfire occurred while villagers observed the Muslim holiday marking the birthday of the Prophet Muhammad in Kaduna state’s Tudun Biri village.

Nigerian military authorities must provide more information on the investigation, compensate victims, and put in place systems and processes to avoid future misfires, said Anietie Ewang, Nigerian researcher with Human Rights Watch.

“There really needs to be a well-thought-out process to ensure accountability and justice for victims of these airstrikes,” said Ewang.

Nigeria’s President Bola Tinubu had said such “avoidable errors are unacceptable and cannot be repeated.” Rights groups and activists also condemned the attack and called for increased scrutiny of the military’s operations in conflict zones.

One major concern has been the proliferation of drones within Nigerian security agencies such that “there is no guiding principle on when these can be used,” Kabir Adamu, an Abuja-based security analyst, told The Associated Press.

“The military will take extra precautions in the future to ensure that non-combatants are safe,” Buba said.