At least three aid workers have been killed in the northeastern Nigerian town of Rann during an attack by militants on a military facility, a United Nations spokeswoman says.
A fourth aid worker may also have been killed and another was feared abducted, the spokeswoman said.
A separate UN source said the attack in Borno state was likely to have been carried out by jihadist group Boko Haram.
All the aid workers were Nigerian nationals, the spokeswoman said.
