Hundreds of people have been killed as troops from Chad seized the Nigerian town of Dikwa from Boko Haram extremists, according to military reports and witnesses.
Boko Haram left hundreds of people dead in Dikwa before fleeing Chadian forces, said Chad spokesman Colonel Azem Bermandoua. One Chadian soldier was killed and 34 were injured, he added.
The United Nations said 16,000 Nigerians fled the fighting into Cameroon.
Elsewhere, Nigerian soldiers fought off a separate attack miles outside the biggest city in north-eastern Nigeria.
Nigerian troops killed 70 Boko Haram fighters to repel an attack on Konduga town, according to a soldier.
Konduga has been attacked many times because it is 35 kilometres (25 miles) from Maiduguri, the biggest north-eastern city and the birthplace of Boko Haram.