A victim of a bomb blast that ripped through United Nations offices in the Nigerian capital of Abuja is loaded into an ambulance. (Reuters)

Local police said they believed the explosion happened after a sedan drove into the building, where hundreds of people were working. The car rammed through through two separate gates as guards tried to stop it. Local media report that many more victims could be under the rubble.

“I saw scattered bodies,” said Michael Ofilaje, a UNICEF worker at the building. “Many people are dead.”

Police are still investigating the cause, but local media reported it was likely a suicide bomber.

Thick black smoke rose from the building after the blast.

The building, located in the same neighborhood as the U.S. embassy and other embassies, looked like it had “a huge hole punched in it,” according to the AP. 

Firefighters and rescue workers go to work after a large explosion struck the United Nations' main office in Nigeria's capital Abuja. (AP)

During the past few months, Nigeria, which is split between a mostly Christian south and Muslim north, has seen assassinations and bombings from a radical Muslim sect called Boko Haram.

Boko Haram wants a strict version of Shariah law implemented in the nation.

“This is very likely the work of Boko Haram,” a security official told Reuters of the bomb blast. It “is a serious escalation in the security situation in Nigeria.”