Nigerian forces backed by airstrikes seized the northeastern border town of Baga from Islamist group Boko Haram on Saturday, the military said, a significant victory in an offensive against an insurgency affecting four African states.

Retaking the town, at Nigeria¡¯s border with Chad, Niger and Cameroon, had been a key objective, given that it had served as the headquarters of a multinational force of troops from all four countries.

¡°We have secured Baga. We are now in full control. There are only mopping up exercises left to do,¡± Defense Spokesman Maj. Gen. Chris Olukolade said by telephone.