A suicide car bomb has exploded at the United Nations building in the Nigerian capital Abuja killing at least 18 people. A hospital in Abuja said 60 people have been brought in many in a critical condition. Witnesses said the bomber drove a car through security barrier and crashed into the reception area of the five-story building detonating the explosives. The UN Secretary General Ban ki-moon has described the bombing as a terrible act. The Nigerian President Good luck Jonathan has condemned the bombing as barbaric, senseless and cowardly. He said the government would spare no effort in bringing the perpetrators to justice. A source at the UN said the Islamic Group Boko Haram had issued a threat against the UN building and security have been stepped up.