A Nigerian military jet has mistakenly bombed a camp for displaced people in the north-east, killing at least 52 people and injuring many more.
Aid workers are among the dead in Rann, with the Red Cross saying six of its employees were killed.
The MSF aid agency said that over 200 people had been injured and appealed for help with medical evacuations.
President Muhammadu Buhari, whose army is fighting Boko Haram militants, expressed dismay and urged calm.
The attack took place near the border with Cameroon, where the military is engaged in what it calls its final push against Boko Haram.
It is thought to be the first time Nigeria’s military has admitted to making such a mistake.
Red Cross spokeswoman Aleksandra Matijevic said that along with the staff killed, more than a dozen of the group’s volunteers, who arrived on Tuesday to deliver food to the thousands displaced people, were wounded.
“Our thoughts are now with the families of our colleagues who have lost their loved ones,” Ms Matijevic said, adding that the Red Cross would continue bringing humanitarian aid to those affected by the conflict.
MSF told the BBC that its organisation also had medical teams working in the Rann camp when the bombs struck.
“More than 50 people have been killed,” said Hugues Robert, head of MSF’s emergency response.
“Our team was there and counted the bodies, and more than 200 people have been wounded following these two different blasts from aerial bombardment,” he said.
MSF said it had teams in Cameroon and Chad ready to treat wounded patients.
Many of the casualties, it said, were believed to be displaced people who had fled from areas where Boko Haram had carried out attacks.