BBC News with Marion Marshall

At least 18 people are now known to have been killed in a suicide bomb attack on a United Nations building in the Nigerian capital Abuja. A radical Islamist group, Boko Ha

ram

, said it carried out the bombing. Karen Allen reports.

The

admission

by the Islamist militant group Boko Haram that it carried out this morning's attack has confirmed the worst fears of security experts.

At around 11 o'clock local time, a car forced its way through two checkpoints and rammed into the UN buildings, exploding on impact. Shards of glass were thrown into the air, and one wing of the UN building collapsed to the ground. A number of dead were being seen dragged from the scene. Dozens more are now being treated in hospital in what the Nigerian authorities describe as a cowardly targeted attack.

The Nigerian President Goodluck Jonathan has said his government will

spare no effort

in bringing the

perpetrator

s to justice. The UN Secretary General Ban Ki-moon described the bombing as a terrible act.

"On this very sad occasion, I extend my deepest sympathies to the victims and their families. The United Nations will

undertake

every possible effort to assist them during this difficult time."

Mr Ban said he would send his deputy Asha-Rose Migiro to Nigeria immediately.

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