The International Safety Organisation, which provides security to foreign non-governmental organisations in the northeast, said in an internal memo seen by Reuters that the vehicles moving between the towns of Rann and Gamboru Ngala hit an improvised explosive device.

The blast led "to the death of 26 individuals and three injuries," it said. 

Borno state police could not immediately comment. 

The insurgents Boko Haram and extremist in the West Africa Province have been battling Nigerian security forces for over 15 years in the northeast and often use improvised explosive devices to target civilians and security forces. 

--Reuters--