Military reports and witnesses say hundreds of people have been killed as troops from Chad seized the Nigerian town of Dikwa from Boko Haram extremists while Nigerian soldiers fought off a separate attack miles outside the biggest city in northeastern Nigeria.

Chad spokesman Col. Azem Bermandoua said Boko Haram left hundreds of people dead in Dikwa on Monday before fleeing Chadian forces. He said one Chadian soldier was killed and 34 were injured.

The United Nations said 16,000 Nigerians fled the fighting into Cameroon.

A Nigerian soldier said Nigerian troops killed 70 Boko Haram fighters to repel an attack Monday on Konduga town. Konduga has been attacked many times because it is 35 kilometers (25 miles) from Maiduguri, the biggest northeastern city and the birthplace of Boko Haram.