Thirty-nine people have been killed in two attacks in recent days in western Niger, near the border with Burkina Faso, Niamey's defence ministry said Saturday.

"Two horrific tragedies happened in the communities of Libiri and Kokorou, criminals cornered by constant operations by defence and security forces launched attacks on defenceless civilian populations," the defence ministry said in a statement.

The "barbaric acts" saw 21 people killed in Libiri and 18 in Kokorou, including children, the ministry said.

The operations took place from December 12 to 14, the statement said without detailing when the attacks happened.

The frontier lands between Niger, Mali and Burkina Faso have long been a hideout for jihadists linked to the Islamic State group and Al-Qaeda, who have waged an insurgent war against the government.

On Wednesday, both the BBC and RFI reported that jihadists had killed 90 soldiers and over 40 civilians in Tera's Chatoumane.

Niger's junta dismissed reports of the attack and deaths as "baseless assertions" and a "campaign of intoxication".