AVA- The attack took place on Monday afternoon at a camp at Inates on the border with Mali, the defense ministry said in a statement. Four soldiers were listed as missing.
Niger, one of the world's poorest countries, lies in the heart of the fragile Sahel region, which is battling an insurgency.
"The attack began with the detonation of two suicide vehicles at the entrance to the camp, followed by gunfire from terrorists who arrived on motorbike," the statement said. "The counter-attack, with air support from our partners [French and American], enabled the enemy to be routed beyond our borders," it said.
"Sweeping-up operations are continuing."
Several "terrorists" were killed, a truck was destroyed by airstrikes and two explosive-laden vehicles were destroyed, it said.
On Monday, a military source, speaking on condition of anonymity, told AFP there had been a twin "car-bomb attack" at the camp and suggested the toll would be high. The base, located in a volatile region, trains Nigerien soldiers to serve in a UN peacekeeping mission in Mali.
Insurgent groups are active in western and northern Mali, spilling over from a long-running militancy in Mali, while Nigeria's Boko Haram is present in the country's southeast.
Last month, the defense ministry said 18 members of Daesh in the Greater Sahara, or ISGS, were killed in a joint operation by US, French, and Niger troops in the southwestern border region of Tongo Tongo.
In October 2017, the ISGS claimed responsibility for a raid that killed four US soldiers and five Nigerien troops in the same region, a mere 20 kilometers from the Malian border. The United States has a big base for drones in the northern city of Agadez and Niger recently gave the Americans permission to arm their drones. The French also have a military base near the airport at the capital, Niamey, and another at Madama in the north.
Niger is part of the so-called G5 Sahel group of five nations set up to manage a coordinated response to the militancy in the impoverished region.
Niamey hosts a major meeting of the African Union from July 4-8, culminating in a summit expected to gather about 50 heads of state or government.