At least 50 people were killed and 120 were injured in a series of airstrikes carried out by the Nigerian army against a refugee camp.
The Nigerian army confirmed the attack on the refugee camp in Rann, located about 1000 kilometres to the north of the Nigerian capital, Abuja, but did not specify the number of casualties.
The army said it had launched a military operation targeting terror group Boko Haram which also "unfortunately" affected civilians as well as members of Doctors Without Borders (MSF) and the Red Cross international committee (ICRC).
ICRC Africa confirmed six of their workers were killed and 13 wounded.
"They were part of a team bringing desperately needed food for more than 25,000 displaced people in Rann," the organisation tweeted.
Two soldiers also were wounded but a final toll is not immediately available.
The mission was based on information that Boko Haram insurgents were gathering, along with geographic coordinates.
It was too early to say if a tactical error was made.
Major General Lucky Iraboreneral, who is the theatre commander for counterinsurgency operations in northeast Nigeria, said the air force would not deliberately target civilians, but there will be an investigation.
This is believed to be the first time Nigeria's military has admitted to making such a mistake.