Jihadists killed 14 security personnel and civilians in an attack on a military base in northeast Nigeria's Borno state on Wednesday, security sources told AFP.Suspected Boko Haram fighters in trucks fitted with machine guns launched a dawn raid on the army base in the town of Damboa, sparking intense fighting.Sources said six soldiers, four police officers and two members of a government-backed militia were killed along with two civilians."We lost six soldiers in the attack while six others were injured," a military officer told AFP on condition of anonymity. The officer claimed 13 insurgents were killed by a fighter jet as they fled the area. The leader of an anti-jihadist militia said the civilians who died were among more than 50 local residents hit by shrapnel after rocket-propelled grenades fired by the jihadists hit nearby homes.Nigeria's decade-long jihadist insurgency has killed 36 000 people and displaced two million others inside the country, and spilled into neighbouring Niger, Chad and Cameroon.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 despite repeated claims from officials that the insurgency has been defeated.The jihadists fighting in northeast Nigeria have split into rival groups with one loyal to longtime Boko Haram leader Abubakar Shekau and another affiliated to the Islamic State group.Damboa lies on the fringe of Shekau's stronghold in the Sambisa forest from where his group has launched repeated attacks on villages and military posts.In November last year, at least 10 Nigerian soldiers were killed and nine injured in a Boko Haram ambush in Muchima village, outside Damboa.