Mali and Niger forces were carrying out a joint operation when a patrol was attacked by Takfiri terrorists near the northeastern town of Tabankort, the army said on social media, Presstv Reported.
According to the military the total toll was "24 dead, 29 injured and material damage" while 17 of the terrorists were killed and a hundred more suspects captured.
The prisoners are in the hands of Niger soldiers, the statement said.
In an earlier statement, which gave a lower death toll, the army said French and Niger forces took part in a counterattack.
Northern Mali fell into the hands of terrorists in 2012 before the militants were forced out by a French-led military intervention.
Since then however, the border regions of Mali, Niger and Burkina Faso have become the theater of repeated clashes with Takfiri militants.
Mali's army has been struggling to contain the elements despite help from France, African neighbors and the United Nations.
Monday's action was another heavy loss for the army which lost a hundred soldiers in two terror attacks in a month in the autumn.