In the capital, the group bombed a crowded fish market on New Year's Eve and attacked a beer garden in May. Hundreds of civilians have been killed this year in more than 70 attacks, the vast majority of them in the north.
Its base, Maiduguri, has been hardest hit, with businesses closing, people shunning public gatherings and motorcycle transportation (used heavily for both people and goods) banned by the state government.
Martin Ewi, an analyst at the Pretoria, South Africa-based Institute for Security Studies, sees Boko Haram's targeting of the U.N. as "a deliberate strategic choice aimed at demonstrating that the group means business."
"The attack on the UN headquarters completes Boko Haram's metamorphosis into an international terrorist group and represents a turning point for the future of terrorism in Nigeria," Ewi wrote. "In reality, this means that moving forward the goal of islamisation or for spreading sharia shall not be confined to Nigeria and that other countries in the region are potential targets."