Nigeria's military says troops have killed scores of Islamic extremists and rescued 20 women and children from captivity even as reports come in of Boko Haram fighters slitting villagers' throats and chopping them to death.

That bolsters reports the insurgents are running out of ammunition and resorting to hit-and-run assaults in the face of a Nigerian offensive against their last stronghold in the northeastern Sambisa Forest.

A military statement Saturday said four camps were destroyed Friday despite land mines that killed one soldier and wounded 10.

Meanwhile, farmer Kwada Abawu said he saw at least 10 people slaughtered before he fled his northeastern village of Kwamda-Kobla on Friday.

Local government chairman Maina Ularamu said no shots were fired: victims were axed to death, some had their heads cut off.