Scores of Boko Haram fighters were among the 400 people arrested by Nigerian soldiers, military authorities in the west African nation said.
The two-week operation on the islands of Lake Chad netted the largest number of arrests, said Colonel Onyema Nwachukwu, adding that the operation included air and ground offensives.
The military said many Boko Haram insurgents were killed, but it did not give details.
Among those arrested were 167 Boko Haram fighters, 67 women and 173 children. The women and children will be handed over to authorities of displacement camps after investigations, the military source said.
Another 57 insurgents were arrested during a separate operation in another part of the troubled region.
Boko Haram has been blamed for more than 20,000 deaths during its eight-year insurgency, which has spilled over into neighbouring countries and created a vast humanitarian crisis with millions displaced and starving.