The claim by Al Qaeda in the Islamic Maghreb that it holds hostages kidnapped more than a month ago fuels fears that the group is expanding its reach.
Five months into the economic crisis, experts predict a years-long recovery.
A conflict could reduce Nigeria's oil output, affecting global oil supply.
In a separate conflict, Congolese rebels declare a cease-fire and plan to join government forces.
The Iraq war dominated his presidency, but it isn't the only signature foreign-policy event of his tenure.
Terrorists have not succeeded in striking on US soil since 9/11. But some say the US focus was too much on a military response, regime change, and a 'with us or against us' mentality.
Widely considered an obstacle to peace, Abdullahi Yusuf announced his resignation on Monday.