The Niger Delta Avengers are a new militant group that has claimed responsibility for a recent wave of attacks on pipelines in Nigeria's oil-rich south.
Amnesty International says the Nigerian army tried to cover up the unlawful killings of members of Islamic Movement of Nigeria, which took place in city of Zaria over a two-day period spanning in December last year.
The army justified the raid by saying that the sect's leader, Sheikh Ibraheem Zakzaky, was trying to assassinate an army official.
In this excerpt, VICE News correspondent Kaj Larsen embeds with an operational air wing provided by private military contractors to the Nigerian military for their assault on the city of Bama.
The Nigerian army set up an outpost in a former girls' secondary school, while Boko Haram used a second school across the road as a staging ground for attacks.
Residents of the Borno State capital expect an attack soon in what could be the largest and most symbolic seizure yet by the group.