Islamic extremists say they have killed more than 40 troops from a multinational force in northeast Nigeria — the fourth attack in three days following a lull as Nigeria's home-grown insurgency confronts a leadership struggle.

The SITE Intelligence Group, which monitors online jihadist activity, cited a communique Tuesday as saying the Islamic State's West Africa Province annihilated "a convoy of the African Coalition Crusader forces" in the town of Malam Fatori. There was no way to independently verify the claim and no word from Nigeria's military late Tuesday night.

Eighteen people were killed Sunday and Monday when insurgents ambushed another convoy, gunned down Christians and beheaded a village head and his son.

Tuesday's was the first Nigeria attack claimed by the IS group since August, when it named a new caliph in Nigeria and provoked a leadership struggle.