Nigerian Islamists killed 14 pro-government youth vigilantes in an attack on the northeastern town of Bama, a local official who attended a mass funeral for the victims said on Monday.
Sunday's attack was one of a spate of deadly assaults by the Boko Haram Islamist sect this month that raises doubts about whether a military offensive against it since May can succeed.
Local vigilante groups run by youth volunteers have been instrumental in helping the military capture Boko Haram members, but they have also made them a target for the insurgents, drawing civilians further into the conflict.
Alhaji Baba Shehu Gulumba, chairman of Bama local council, told journalists in the nearest main city of Maiduguri that insurgents disguised as soldiers lured the youths into a trap. Nine others were wounded.
"They were on guard duty when the sect members dressed in military camouflage came and told them that they were needed at a meeting nearby," he said. "When they had been lured away from their duty posts they were then attacked and killed."
Bama is in Borno state, the centre of the insurgency. The town is not far from a mountainous area along the Cameroon border where many Boko Haram fighters are believed to be holding out, after being cleared from other areas by Nigerian forces.
Their four-year battle to revive an ancient Islamic caliphate in religiously mixed Nigeria remains the main security threat to Africa's top oil producer.
The military announced a week ago that Boko Haram's leader Abubakar Shekau may have died between late July and early August from bullet wounds he received during a gun battle weeks before.
If he did die, not only has it failed to stem the violence, but deadly attacks are actually up on a month ago.
Last Monday, suspected Islamists killed 44 people in the village of Bemba, near Lake Chad, an area of porous borders with Niger, Cameroon and Chad that was an Islamist stronghold before President Goodluck Jonathan declared a state of emergency in the northeast in the middle of May.