Nigerian forces rescued 360 captives, including women and children from a Boko Haram mountain hideout in Borno State.
Two infants succumbed to the 'harsh conditions' of Boko Haram captivity in the Mandara mountains, the army says.
The group includes many women and children who were abducted in March from an area close to Cameroon.
Communities in the Lake Chad Basin face rising violence amid economic hardship and weak governance.
No group claimed responsibility for the raid, which bore the hallmark of the Boko Haram group.
A fishermen's leader tells the BBC that 40 people are feared dead - either in the strikes or drowning as they tried to flee.