Niger and Chad have reportedly launched a joint air and ground offensive to take on Boko Haram in north-eastern Nigeria, officials said.
The operation in believed to be targeting militants in Borno state, reported the BBC.
It came as Nigerian officials dismissed Boko Haram's pledge of allegiance to the Islamic State (IS) as a reaction to military pressure from Nigeria and its allies.
In a message released online on Saturday, Boko Haram leader Abubakar Shekau urged Muslims everywhere to pledge loyalty to IS leader Abu Bakr al-Baghdadi.
