ABUJA, Nigeria, Aug. 26 (UPI) -- A suicide car bomb collapsed an interior wall at the U.N. building in Abuja, Nigeria, Friday, killing at least 18 people and injuring others, officials said.
U.N. officials said the number of dead was likely to rise considerably, The New York Times reported.
Witnesses reported seeing Red Cross officials taking bodies from the building to the National Hospital after the 11 a.m. blast, CNN reported.
Rescue officials were at the building helping to extract people from the rubble, witnesses said.
The National Hospital in Abuja treated "many casualties, lots of them seriously injured," a hospital official told CNN.
The hospital called in all doctors and nurses to handle the emergency. Members of the staff and relatives of the victims donated blood to deal with a shortage.
Nigerian President Goodluck Jonathan said the bombing was a "barbaric, senseless and cowardly attack."
U.N. Secretary-General Ban Ki-moon, speaking to reporters in New York, condemned the attack, saying, "This was an assault on those who devote their lives to helping others."
Yushau Shuaib, a spokesman for Nigeria's National Emergency Management Agency, said the vehicle used in the bombing was able to pass through two security gates before it exploded near the building's reception area, CNN said.
"This brutal act has killed and injured many innocent people, and I utterly condemn those who have carried it out," U.K. Foreign Secretary William Hague said.
"Around the world, the U.N. works for peace, security and international cooperation and an attack on the U.N. is an attack on these principles."
The BBC reported smoke billowed from the building and the blast shattered all of its glass.
Witnesses in the U.N. building told CNN there was an explosion, and then an internal wall collapsed on some people.
Police sealed off the area.
The building housed the main U.N missions operating in Nigeria and could have had up to 400 people inside when the bomb went off, CNN said.
Bomb squad officers and other security teams were dispatched to the scene, deputy police spokesman Yemi Ajayi said.
No one had claimed responsibility for the bombing, officials said.
U.S. President Barack Obama condemned the attack.
"An attack on Nigerian and international public servants demonstrates the bankruptcy of the ideology that led to this heinous action," Obama said.