The U.S. has also authorized the deployment of 300 troops to Cameroon to fight the insurgents
Mohammed allegedly colluded with Sambo Dasuki to steal arms money earmarked for fighting Boko Haram.
The IMF managing director is visiting Nigeria as the country struggles to deal with a global oil slump.
More than 200 girls remain missing despite Buhari's claim that Boko Haram had been "technically" defeated.
Too often the default has been to shoot first and ask questions later, says John Campbell.
The U.K. has promised to double the number of British military personnel deployed in Nigeria in 2016.
The Nigerian president claims Boko Haram has been "technically" defeated despite an upsurge in attacks.
At least 300 Shiites were killed in clashes with the army in Zaria, northern Nigeria.
More than 2,000 schools in Nigeria, Cameroon, Chad and Niger remain closed due to the conflict with Boko Haram.
Young girls sent out as bombers by the Nigerian militants are often unwilling, a U.N. expert said.
At least 60 people died in clashes between Shiite Muslims and Nigerian soldiers on Saturday.
The group has carried out attacks across the borders of neighboring countries.
The six-year insurgency has internally displaced more than 2 million Nigerians.
The army has a December deadline to reclaim all Boko Haram-held territory.
Hassan John is a Christian pastor in Jos, central Nigeria. Boko Haram wants him dead.
The country is seeking to reduce pressure on its crammed prisons.
The series of suicide bombings in recent months prompted Chad last month to declare a state of emergency.
The aid organization already works in Boko Haram-held territory in Nigeria.
The government has said it cannot guarantee all attacks will stop by the New Year.
The Nigerian Army has launched ground and air strikes against the group in their Sambisa Forest stronghold.