UN chief Ban Ki-moon said the attack was "an assault on those who devote their lives to helping others"
Speaking before Boko Haram's statement, President Goodluck Jonathan reaffirmed his government's "total commitment" to combating terrorism, and said his administration would "spare no effort to bring the perpetrators to justice".
Speaking before Boko Haram's statement, President Goodluck Jonathan reaffirmed his government's "total commitment" to combating terrorism, and said his administration would "spare no effort to bring the perpetrators to justice".In Friday morning's attack, a car crashed through two security barriers and rammed into the building's reception before exploding, witnesses said.
Hospitals are said to be overwhelmed by the number of injured and have appealed for blood donations.
Boko Haram, which is fighting for the establishment of Sharia law in Nigeria, also said it carried out a car bombing at police headquarters in June.
A UN official in Nigeria, who spoke to the BBC on condition of anonymity, said the UN had stepped up security at all its buildings in Nigeria in the past month after receiving information that the UN could be targeted by Boko Haram.
Analysts say that the scale and target of the attack could point to a link with international terror groups.
