Niger's defence ministry said "heavily armed men" had attacked troops serving under the anti-jihadist Almahaou ("whirlwind") operation near the town of Banibangou in the Tillaberi region on Tuesday afternoon.

Four more soldiers were injured in the attack, the ministry said, with search operations continuing.

"On the enemy's side, several terrorists were killed and equipment destroyed," it added in a statement, without giving further details on the circumstances of the attack.

Tillaberi is located in the flashpoint "tri-border" region between Niger, Mali and Burkina Faso, the site of frequent bloody attacks by jihadist groups.

On Saturday, 16 Nigerien soldiers were killed and another reported missing after armed men attacked a patrol in the Tahoua region, also close to Mali.

The vast desert region, east of Tillaberi, is similarly a regular target for jihadists who target civilians as well as troops.

On March 21, several hamlets in Tahoua's Tillia area were struck by coordinated attacks that left 141 people dead, according to the official toll -- the most deadly presumed jihadist assault in Niger in years.

Niger is struggling with both the spillover of Nigeria's Boko Haram extremist movement in its southeast, and that of jihadists affiliated with the Islamic State group and Al-Qaeda in its west.

It is the world's poorest nation, according to the UN's development rankings for 189 countries.