A car bomb has exploded at the main United Nations building in Nigeria's capital Abuja, killing at least 18 people in one of the deadliest assaults on the international body in a decade.
A radical Muslim sect blamed for a series of attacks in the country admitted the attack - a major escalation of their sectarian fight against Nigeria's weak central government.
The brazen assault in a neighbourhood surrounded by heavily fortified diplomatic posts represented the first suicide attack to target foreigners in oil-rich Nigeria, where locals already live in fear of the radical Boko Haram sect.
The group, which has reported links to al Qaida, wants to implement a strict version of Sharia law in the nation and is vehemently opposed to Western education and culture.
"It is an attack on the global community," said Viola Onwuliri, a junior Nigerian foreign minister, as she looked at the bomb site.
A sedan laden with explosives crashed through two gates at the exit of the United Nations compound on Friday morning as guards tried in vain to stop it, witnesses said.
The suicide bomber inside drove the car through the glass front of the main reception area of the building and detonated the explosives, inflicting the most damage possible, a spokesman for the Nigerian National Emergency Management Agency said.
"I saw scattered bodies," said Michael Ofilaje, a Unicef worker at the four-storey building, which he said shook with the explosion. "Many people are dead."
At least 18 people died in the attack. Nigerian health minister Mohammad Ali Pate made a public appeal for blood donations, saying there were at least 60 injured people alone at the nearby National Hospital.
"We condemn this terrible act utterly," UN Secretary-General Ban Ki-moon said. "We do not yet have precise casualty figures but they are likely to be considerable. A number of people are dead; many more are wounded."