"There are dead soldiers and another dozen who were wounded in this Boko Haram attack in Toummour," one security source told AFP, while another source said "at least five soldiers and one civilian" had been killed.
Toummour is located in the Diffa administrative region, which lies on the frontier with Nigeria and Chad. It has suffered a string of deadly Boko Haram attacks since February 2015, although the area has been relatively calm in recent months.
It did not detail the number of military casualties.
Boko Haram launched an insurgency in northeast Nigeria in 2009 that in 2015 spilt into Niger. It also affects the country's other neighbours, Chad and Cameroon.
Overall, more than 20,000 people have been killed and more than 2.6 million displaced in the conflict.