The sources stated: "Extremists linked to ISIS killed 15 security personnel in an ambush set up for the convoy of the governor of Borno state in the troubled northeastern Nigeria."
Sources told Agence France-Presse that eight policemen, three soldiers and four members of a government-backed militia were killed in an attack on cars carrying the governor of "Borno" state, Babagana Omara Zolom, near the town of Baga on the banks of Lake Chad.
The mercenaries fired machine guns and rocket-propelled grenades as the convoy was passing by a village close to the headquarter of the Multinational Joint Task Force (MNJTF), a military alliance of forces from Nigeria, Niger, Chad and Cameroon.
A source said: "The ruler escaped unharmed, but 15 security men in the convoy were killed in a fierce battle with the terrorists.".
One of the sources said that the governor who was on his way to Baga as part of preparations for the return of thousands of residents of this city who were expelled by extremists from it in 2014 stated that Zolom was evacuated from the scene of the attack by a helicopter to a safe place before arriving in Baga in another convoy under tight security measures.
ISIS-affiliated West Africa State (ISWAP) maintains most of its camps on islands in Lake Chad and the area is known as a stronghold for the jihadists.