Niger's defence ministry said Sunday that four of its soldiers had been killed the day before in twin "terrorist" attacks in the country's southeast, the day after President Mohamed Bazoum was sworn in.

"Several terrorists" had been killed in the simultaneous Saturday morning attacks against military positions, the ministry said using a term usually used to describe jihadists.

It added that the "heavily armed" attackers "came from a neighbouring country" in a reference to Nigeria, where groups linked to Boko Haram are active.

The first president installed in a democratic transition of power in Niger's six decades of independence from France, Bazoum on Friday lashed out at jihadist "war crimes" in his country as he took office.

Niger is being hit by insurgents linked to Al-Qaeda or the so-called Islamic State (IS) crossing from Mali and Burkina Faso in the west, and by Boko Haram crossing from Nigeria in the southeast.

Thousands of people have been killed, and hundreds of thousands have fled their homes.

Since the start of this year alone, more than 300 people have been killed in three attacks in the west.

Hoping to improve security through cooperation with neighbouring states, especially Mali, Bazoum has previously ruled out any talks with the jihadists.

"We cannot envisage any dialogue of any kind so long as there is a single Nigerien jihadist chief, a single jihadist base on our territory," he said in a recent interview with French media outlets RFI and France 24.

As well as the jihadist insurgency, Niger's government claimed it had thwarted an "attempted coup" after gunfire broke out near the presidency in capital Niamey early Wednesday.