Nigeria's new president, who met in late July with President Obama, has stepped up efforts to rescue hostages taken by Islamist militant group Boko Haram.
Six weeks into his term, President Buhari has replaced his military service chiefs and appointed a new national security adviser. Critics have attacked what they see as his slow pace in making appointments.
Two bomb attacks on the city of Jos have left up to 67 people dead on Sunday in a recent surge of attacks by the Islamist militant group. President Buhari vowed to stamp out the group in his inauguration address just over a month ago.
An estimated one-third of government spending goes towards Chad's vaunted army, a dependable regional policeman and the pride of the people. But a taste of stability, and oil money, has Chadians wanting more.
Muhammadu Buhari is the first opposition candidate to unseat an incumbent in a presidential election. He has vowed to strike hard at Islamist militants in northern Nigeria.
Nigeria's Boko Haram pledged allegiance last week to the self-proclaimed Islamic State, which is fighting for control of the Iraqi city of Tikrit.
The militant Islamist group killed 68 in Njaba, but has suffered setbacks in some areas after Nigeria teamed up with other West African countries to launch air and ground attacks.