At least 16 killed by bomb attack on UN's Nigeria base

Muslim group claiming responsibility for atrocity says 'this is only the beginning'

A radical Muslim sect last night claimed responsibility for a bomb attack that gutted the United Nations head office in the Nigerian capital, Abuja, killing at least 16 people and leaving a dozen injured.

Boko Haram, which has carried out a series of terrorist attacks in northern Nigeria in the past year, called several radio stations to claim that, "this is only the beginning".

It was the first time that the group had chosen an international target. It is understood that most of the victims were Nigerian.

Eyewitnesses said that at 10am yesterday morning a vehicle that was "larger than a car" entered the compound – in which 26 UN agencies have offices – through the exit gate. The vehicle then drove straight into the lobby area of the L-shaped building in which about 400 people worked.

One office worker who was at her desk on the fourth floor described a "loud noise and dark smoke".

Kori Habib said: "All the windows broke immediately, the walls started coming down and then the ceiling. We held hands to reach the stairs and when we got to the ground floor we were having to walk around bodies to reach the exit."

Last night hospitals in Abuja were calling on members of the public to donate blood. UN officials were reluctant to speak about the incident until they had successfully traced all the members of staff.

The explosion punched a huge hole in the building. Construction workers

brought three large cranes to the site within hours of the attack, trying to pull away the concrete and rubble to find survivors. Others at the site stood around, stunned, as medical workers began carrying out what appeared to be the dead.

"This is getting out of hand," said one UN staffer. "If they can get into the UN House, they can reach anywhere."

Ali Tikko, who was in a building 100 yards from the site of the blast when it occurred, said: "I heard one big boom. I see a number of people lying on the floor – at least four or five. I cannot see if they are dead. There are a lot of security around."

The attack was condemned by US President Barack Obama as well as by United Nations Secretary General Ban Ki Moon, who said the victims were "people who have dedicated their lives to others".

Nigerian President, Goodluck Jonathan, said the blast was "an attack on global peace and security". Speculation over Boko Haram's motive included anger at the Nigerian government's move on Tuesday to recognise the Libyan Transitional National Council.

There have been reports that the group, which was created around 2002, had received training in Libyan camps and support from Gaddafi's regime.

But an organisation spokesman said in June that members had trained in Somalia, which suggests a link to Al Qaeda-affiliated groups. The last time a similar target was bombed in Africa was in August 1998 when simultaneous suicide bombs exploded at the US embassies in the Kenyan capital, Nairobi, and the Tanzanian city of Dar es Salaam. They killed more than 220 people and were linked to the Egyptian Islamic Jihad and Osama bin Laden.

Boko Haram, from north eastern Nigeria, launched its armed wing in 2009 and has claimed responsibility for terror attacks in Nigeria. It wants Sharia rule and opposes secular government.

In July, 2009 it staged an armed uprising in Maiduguri, which was crushed by the military at the loss of some 800 lives. Since then, it has chosen targets linked to Nigerian security, chiefly ambushing military patrols. It was blamed for the suicide bombing of the Abuja police headquarters last month.