The ISWAP group carries out regular attacks in Buni Yadi region on soldiers and travellers, with the violence spilling over into Borno state.
Thirteen soldiers have died in an ambush by jihadist fighters from the Islamic State West Africa Province group in volatile northeastern Nigeria, two army sources told AFP on Monday.
Heavy gunfire and rocket-propelled grenades hit a military convoy in Gazagana village, 30 kilometres from Yobe state capital Damaturu on Saturday.