Six soldiers were killed and three others wounded on Wednesday amid a suspected Boko Haram attack in Southeast Niger, the interior ministry said in a statement.
Boko Haram militants suffered heavy setbacks in recent months, due to counter attacks by national armies from the region.
The statement from the interior ministry said that the soldiers were killed in an ambush "by Boko Haram terrorists [militants]" at around 6am as they were patrolling some 20 kilometres (12 miles) from Diffa, the region near the Nigerian border.
More than 17,000 people have been killed since Boko Haram began its militancy in 2009, in northeast Nigeria.
At least 2.6 million people have fled their homes since the violence began, but some of the internally displaced have returned home after troops began the fight-back last year and recaptured territory.
A regional joint task force involving troops from Nigeria, Chad, Cameroon, Niger and Benin are conducting intense operations to eradicate the militants.