The jihadist group Islamic State West Africa Province (Iswap) has said its fighters killed at least 10 Nigerian soldiers in the town of Magumeri in the north-east.
Security sources have confirmed the attack, but not the death toll.
Reports suggest the militants arrived in several trucks fitted with machine-guns and overran the army’s positions.
Iswap also said 10 Nigerian troops were killed in an ambush on Tuesday near the fishing town of Baga.
The Nigerian military has not commented on the attacks but said on the same day its fighter jets and helicopter gunships had killed a number of jihadists in another area of Borno State.
Iswap is an offshoot of Boko Haram, and pledges loyalty to the Islamic State (IS) group.