The Burkinabe army acknowledged on Wednesday that civilians were killed in airstrikes against "terrorist groups" in eastern Burkina Faso, without specifying the number.
Locals however told the AFP that "around 30" were killed.
"Targeting actions aimed at terrorist groups responsible for several cases of abuse were carried out in several localities (Djamanga, Djabiga, Mandeni, Bounou, Obiagou, Pognoa-Sankoado) in the eastern region," the army said in a statement.
"During these operations, which enabled the neutralisation of several dozen terrorists, the strikes, unfortunately, caused collateral victims among the civilian population," it added.
The victims, whose number was not communicated by the staff, "were near a terrorist hideout on the Kompienga-Pognoa axis" when they "were unfortunately fatally hit by projectiles", the text said.
Local residents interviewed by AFP by telephone from Ouagadougou said that "around thirty civilians", mostly women, were killed in the army strikes.
"They were gathered for the inauguration of a mill when the tragedy occurred," said one of them on condition of anonymity.
The staff said that an investigation "was immediately opened to determine who was responsible" and offered its "sincere condolences to the families and friends of the victims". It assures them of its "commitment to collaborate fully with the competent services and the population to shed light on this unfortunate incident".
For several months, the Burkinabe army has been conducting multiple air operations against armed jihadist groups.
It admitted accidentally killing a civilian on 11 June during an "air action" against a group of armed traffickers in the Centre-South region. An investigation had been opened by the military prosecutor.
Burkina Faso, where the military took power in January promising to make the fight against jihadism their priority, is facing, like several neighbouring countries, the violence of armed jihadist movements affiliated to Al-Qaeda and the Islamic State group, which have killed thousands of people and displaced some two million since 2015.