Nigeria's spokesman for operations in the northeast, Mike Omeri, said cooperation between Chadian and Nigerian forces had brought some major military adding that successes and any issues would be resolved via existing command structures.

But the Chadians say there have been no joint operations between the two forces. Chad's offer to join a Nigerian offensive to capture Baga, site of one of Boko Haram's worst atrocities in January, was rebuffed, Bermandoa said.

Officials from Chad, Niger and Cameroon say lack of cooperation from Nigeria has for months hampered efforts to put together a regional taskforce against Boko Haram.

Chad was compelled to take unilateral action in January, under a deal that allows it to pursue terrorists into Nigeria, after Boko Haram violence started to choke off imports to its economy.