"Two of our men were killed by terrorists on Saturday night in an attack on one of our checkpoints, 60 kilometres (37 miles) southwest of Gao," a military official told AFP on condition of anonymity.

The word "terrorists" is regularly used to refer to Islamist militants, in a region struggling to battle a grinding jihadist insurgency.

Another military official said that two soldiers were killed and another was injured.

They were ambushed as they as moved between positions at the checkpoint, a security official said, also on condition of anonymity.

Since independence and jihadist rebellions broke out in the north in 2012, Mali has been embroiled in a complex conflict that has left thousands of civilians and fighters dead, despite the intervention of UN, African and French forces.

Some of the groups fighting for independence signed a peace deal in 2015, but the Sahel country is still targeted by attacks from groups linked to al-Qaeda and the Islamic State.

The violence has also crossed the borders into neighbouring Burkina Faso and Niger.