An apparent suicide car bombing has hit the UN building in Nigeria's capital, Abuja.
The explosion destroyed the lower floors of the building and left at least 16 people dead. Dozens of others have been injured.
Although no one has yet claimed responsibility for the attack, an anonymous UN official in Nigeria told the BBC that the UN increased security at the building after receiving a tip-off last month that it could fall under attack by West African Islamist group Boko Haram.
Boko Haram, a group calling for the implementation of Sharia law in Nigeria, was blamed for a car bombing at police headquarters earlier this year. Nigerian government officials have blamed "terrorists" for today's attack.
The area around the building has been sealed off by police, and an operation is underway to clear up the heap of rubble, making sure no one is trapped.
Nigerian Minister of State for Foreign Affairs Viola Onwuliri has called the bombing, which took place at about 11am local time, "An attack on the world".
About 400 people are said to work in the building, but it's uncertain how many were there at the time of the attack.
A Unicef worker at the building , Michael Ofilaje, said that he saw "scattered bodies" and overwhelmed local hospitals are calling for blood donations.