Attacks on police officers are becoming commonplace . Yusuf advocated the institution of Sharia law throughout the northern states and opposed democracy . Police believe the Islamist group Boko Haram was behind the attacks . The government has been blamed for a wave of violence .
Attacks on police officers are becoming commonplace . Police believe the Islamist group Boko Haram was behind the attacks . The government has been blamed for a wave of violence .