Islamist insurgent group Boko Haram ambushed Nigerian soldiers in the northeast of the country, killing at least five and injuring more than a dozen, sources told Reuters on Sunday.

The sources said the death toll could increase as a number of soldiers were still missing after the attack on Thursday in Damboa, in Borno state in northeastern Nigeria.

The soldiers had gone to the area to clear a Boko Haram camp, but were ambushed, the sources said.