At least five Nigerian soldiers were killed in an ambush by Islamist insurgent group Boko Haram, with the attack also leaving scores others injured.

While quoting local sources, Reuters news agency reports that the death toll could increase as a number of soldiers are still missing after the attack which happened on Thursday in Damboa in the northeastern Borno state.

The soldiers had reportedly gone to the area to clear a Boko Haram camp, but were ambushed by the insurgents.

The general commanding officer, Brigadier General Bulama Biu, confirmed a confrontation between troops and Boko Haram, but said there was “no casualty on the part of troops.”

Three military sources and three fighters with armed vigilante group Civilian Joint Task Force (CJTF) said the bodies of five soldiers had been recovered, and that 16 fighters, including 14 soldiers and two civilians, were injured. The sources said multiple fighters were still missing.

Boko Haram has waged an insurgency in Nigeria and West Africa for more than a decade, killing tens of thousands and displacing millions others.

Crushing the militant group remains a focus for the Muhammadu Buhari administration. The president earlier this year pledged new tactics in the fight against terrorism, urging the West African states to unite forces in order to wipe out the group.