At least 11 people have been killed by Boko Haram fighters in a raid on a camp for civilians displaced by the group's violent campaign, military and vigilante sources said.
The knife-wielding attackers, moving under cover of night, targeted people in the town of Banki, 130km southeast of the city of Maiduguri in Borno state, the epicentre of the eight-year conflict with the armed group.
"At around 12:30am (23:30 GMT on Thursday) this morning, some Boko Haram terrorists broke the barricade securing the IDP camp from the rear towards the Cameroon border and entered to seize food from IDPs," a senior military officer, who declined to be named, told AFP news agency.
"They killed 11 IDPs and wounded two in the attack," the military officer said. The raiders also stole food aid rations given to those living in the camp, said the officer.
Adamu Ahmad, a member of a vigilante group charged with protecting the Banki camp, confirmed the incident.
The fighters used knives to kill their victims instead of firearms to avoiding alerting soldiers at a military base adjacent to the camp, Ahmad said.
Soldiers expelled the attackers from the camp after the fighters raised the alarm.
Boko Haram is reported to be running desperately low on supplies after Nigerian security forces successfully cut off supply lines to the group's bases.
"We have reason to believe they most likely acted on a tip-off from insiders," said the officer who suggested that wives or children of Boko Haram fighters may have infiltrated the camp disguised as displaced people to conduct reconnaissance.
Banki was initially an area of relative safety for those fleeing Boko Haram since the camp opened in March 2015. But it has been repeatedly targeted by Boko Haram suicide attacks.
In April last year, at least seven people were killed at the camp in a suicide bomb attack carried out by two women.
In January, a girl, thought to be 10 years old, died in a botched suicide attack after the explosive vest she was wearing detonated outside the camp.
Boko Haram is fighting to overthrow the government and establish an Islamic state in Nigeria's mainly Muslim north.
At least 20,000 people have been killed in violence since 2009 and more than 2.6 million people have been left homeless.
More than five million people are starving as the fighting has devastated farmland, leaving farmers unable to sow or cultivate crops for several years.
Source: News agencies