Eighteen soldiers were killed when "terrorists" struck an army camp in western Niger, the government said Tuesday, adding the US and France had provided air support to help repel the assault.
The attack took place on Monday afternoon at a camp at Inates on the border with Mali, the defence 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 Islamist 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 air strikes and two suicide 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 jihadist campaign in Mali, while Nigeria's Boko Haram is present in the country's southeast.
Last month, the defence ministry said 18 members of the Islamic State group in the Greater Sahara (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 which killed four US soldiers and five Nigerien troops in the same region, a mere 20 kilometres (12 miles) 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 jihadist insurgency 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.