A military patrol vehicle hit a mine on the highway 10 kilometers from Banki in Borno state late Thursday, killing three soldiers and seriously injuring four others, said the sources.
A truck carrying residents from the regional capital Maiduguri to Banki for governorship and state assembly elections on Saturday was also caught in the blast, with seven passengers sustaining shrapnel injuries.
"Three soldier died in the explosion and four others were badly injured while seven civilians were also injured," anti-jihadist militia Usman Hamza said.
Hamza accused the Islamic State West Africa Province (ISWAP) group, which is active in the region, of planting the bomb.
A military officer and another militia member who asked not be to identified gave the same toll.
The military did not immediately respond to a request for official comment.
Banki, 130 kilometers southeast of Borno state capital Maiduguri, houses some 45,000 people displaced by the jihadist conflict in a sprawling camp.
ISWAP and rival Boko Haram have launched several attacks in and around Banki, targeting troops and the displaced.
The decade-long jihadist conflict has killed 40,000 people and displaced around two million from their homes in the northeast, according to the UN.
The violence spread to neighboring Niger, Chad and Cameroon, prompting the creation in 2015 of a regional military coalition to fight the militants.
Fatal Blast in Northeast Nigeria
KANO, NIGERIA - Three Nigerian troops were killed and 11 other people, including seven civilians, were injured by a highway bomb in northeast Nigeria near the border with Cameroon, where jihadists are active, military and militia sources told AFP Friday.