The United Nations Security Council has issued a statement denouncing as a "heinous crime" the bombing of the UN headquarters in the Nigerian capital, Abuja, that has killed at least 18 people.
The August 26 car bombing has been claimed by Boko Haram, which is described as a radical Muslim sect that has been waging a sectarian battle against Nigeria's central government.
Boko Haram is translated from the Hausa language to mean "Western education is sinful."
UN Secretary-General Ban Ki-moon said 26 UN humanitarian and development agencies were housed in the compound. Hundreds of people were at work there at the time of the attack.
Ban described the attack as an assault on those who devote their lives to helping others, and said the UN condemns it “utterly.”
Ban added that the attack would not deter the UN from doing vital work for the people of Nigeria and the rest of the world.
U.S. President Barack Obama is among world leaders who have condemned the attack. Obama said in a statement that "an attack on Nigerian and international public servants demonstrates the bankruptcy of the ideology" of the militants who carried out the attack.
Mike Zuokumor, police commissioner for the Abuja region, told journalists that a suicide bomber was behind the blast, which he said occurred when a car laden with explosives rammed into the building.
"[A] vehicle, loaded with explosives, drove against traffic, entered the exit gate smashed it, got to the second gate, smashed it, went to the reception and detonated, and the man inside the vehicle died," Zuokumor said.
Footage shows the building badly damaged.
Nigeria's ambassador to the United Nations, Joy Ogwu, told reporters that her government considered the attack to be "not only on the civilian population, but especially on the UN family, the UN as an institution."
Ogwu added that she believed the attack added "a new dimension to threats, not only on the domestic front, but internationally. This is a transnational crime. Terrorism is a transnational crime, and Nigeria unequivocally condemns every act of terrorism."
European Union President Herman Van Rompuy denounced the attack as "senseless" and "brutal."
Boko Haram Suspected
An unidentified UN official in Nigeria told the BBC that the UN had received information last month that it could be targeted by Boko Haram -- a radical group that wants to establish an Islamic state. Security was stepped up in response.
A car bombing at Abuja's police headquarters in June was blamed on Boko Haram, and the group has stepped up attacks in recent months.
Alex Vines knows the UN's Abuja headquarters well in his work as head of the Africa program at the London-based Chatham House think tank.
"It's a big building that clusters many of the different UN agencies that are operating out of Nigeria," he told RFE/RL. "And if this whole wing has collapsed, which is what the photographs I've seen seem to confirm, I can but fear that many people including some I know may have been injured and possibly killed."
Nigeria, with a population of 150 million, is split between a largely Christian south and a Muslim north.
The oil-rich country faces terrorism threats on multiple fronts.
The Movement for the Emancipation of the Niger Delta, which has grievances over redistribution and issues of self-determination, was behind bomb attacks in October 2010 aimed at the celebrations that marked 50 years of independence.
Today's attack is the latest in a series of deadly bombings of UN buildings in recent years.
In 2007, a car bombing at the UN building in Algiers killed at least 41 people.
In 2003, 22 people were killed by a bomb attack at the UN building in Baghdad, including UN envoy Sergio Vieira de Mello.
with agency reports