ISWAP militants used Yugoslav-Serbian mortars to strike Nigerian Army camps.
Suspected Boko Haram militants killed at least 20 people in attacks on two villages in northeast Nigeria.
Boko Haram has kidnapped over 400 women and children in northeastern Nigeria and is demanding a £2.7 million ransom within 72 hours.
Nigerian police have rescued 18 bus passengers abducted last week, including eight students traveling for university entrance exams.
Gunmen abducted students from a bus in Nigeria's Benue state on Friday, officials said, amid a surge in nationwide kidnappings.