Six Nigerian soldiers were killed in an ambush by terrorist gunmen in the restive northeast on Sunday, military sources told AFP.

The assailants opened fire on an army convoy near the village of Mayanti, near the border with Cameroon, in an area plagued by attacks by insurgents.

“We have lost six soldiers in an ambush by Boko Haram terrorists,” one officer told AFP.

A second source, giving the same toll, said the military convoy had been on its way to the nearby town of Banki when it was attacked with heavy gunfire and rocket-propelled grenades.

The decade-long extremist uprising has killed 36,000 people and displaced about two million from their homes in northeast Nigeria.

The United Nations has complained of a surge in violence in the conflict zone in recent weeks.

Anger has been growing among local residents about the army’s failure to stem the attacks.

The military has repeatedly claimed that the insurgency has largely been defeated but attacks against civilians and soldiers continue on a near-daily basis.

The conflict has spread to neighbouring Niger, Chad and Cameroon, prompting a regional coalition to fight the insurgents.

The militants fighting in northeast Nigeria have split into rival groups, with one loyal to long-time Boko Haram leader Abubakar Shekau and another affiliated to ISIS.