"Witches and wizards in the country are ready to help restore Nigeria’s lost glory,” according to their spokesman, Dr. Okhue Iboi.
According to Amnesty International, detention facilities have “torture chambers” devoted to abusing prisoners.
Residents of the Borno State capital expect an attack soon in what could be the largest and most symbolic seizure yet by the group.
Nigeria's government is facing even more criticism over its inability to prevent kidnappings and attacks in the country's northeast.
The Nigerian government has been accused of collusion with and criticized for inaction when it comes to combating Boko Haram.