Security sources in north-east Nigeria say at least nine soldiers and two members of a civil defence militia have been killed by jihadi militants.

They told the French news agency that several more civilians are missing, presumed killed or abducted.

The extremists used guns and grenades to ambush a civilian convoy of more than 100 vehicles under military escort near Damboa in Borno state – close to a forest enclave where Boko Haram militants have a base.

Their insurgency, characterised by frequent ambushes, has killed 36,000 people in a decade and spread to three neighbouring countries.