By Felix Onuah
ABUJA (Reuters) - United Nations Deputy Secretary-General Asha-Rose Migiro visited the wounded on Sunday from a bomb blast at the U.N. headquarters in Nigeria that killed at least 23 people and injured dozens.
Friday's car bomb blew out windows, gutted a lower floor and set the building alight in one of the most lethal attacks on the world body in its history.
There has been no confirmed claim of responsibility for the attack but security sources suspect the violent Islamist sect Boko Haram, which has been blamed for almost daily bomb and gun attacks on security forces and civilians in the northeast.
A U.N. spokesman accompanying Migiro at the hospital where the victims were being treated said the death toll had risen to 23, from an earlier estimate of 19 given by emergency services.
That would make it more deadly than the truck bomb attack on the U.N. headquarters in Baghdad in 2003 that killed 22 people, including U.N. envoy Sergio Vieira de Mello.
"We are working as a team to ensure that the injured do get all the treatment that they require," Migiro said after visiting the hospital, where she shook hands and patted the backs of the wounded.
"For people who had lost their lives we are working to see how they are going to be put to rest," she said.
Migiro later met with President Goodluck Jonathan, who has also visited the bomb site but declined to speculate on who could be behind the attack.
If Boko Haram, whose name means "Western education is sinful" in the northern Hausa language, was responsible, it marks an increase in the sophistication of its attacks and an escalation from local to international targets.
Migiro said the bombing was "a shocking incident, an attack on global peace and communities."
"I have looked at the ripped-up gate. It is amazing how this happened and we are grappling with that, now ... an investigation is under way ... We will see what we have to do better," added Migiro, who was accompanied by U.N. Security Chief Gregory Starr.
Analysts, including London-based consultancy Songhai Advisory, on Friday questioned how the bomber was able to slip past two U.N. security barriers with apparent ease.
After meeting with Migiro, Jonathan pledged in a statement from the presidency to offer temporary accommodation and help in the reconstruction of the building so the U.N. could "continue doing the good humanitarian work you have been doing."
"He commended ... all efforts to bring relief to those affected by this condemnable act of destruction," the statement said.
Most of the dead were Nigerian, but a Norway official confirmed one of its citizens was also killed. A U.N. official said the organization expected to be able to release the names and nationalities of the dead later on Sunday.
The car's driver died in the blast, possibly making it Nigeria's first suicide bombing.
BOKO HARAM, AQIM OR BOTH?
The BBC said Boko Haram had contacted it to take responsibility for the attack, but such claims are hard to verify because the sect's command structure is opaque and many people claim to speak on its behalf.
Its activities used to be confined to the remote northeast, on the threshold of the Sahara desert, where it has killed more than 150 people in bombings and shootings this year, although it claimed a car bomb at police headquarters in Abuja in June.
It says it wants Sharia law more widely applied in Nigeria, beyond the mostly Muslim north where some states have it, but until Friday had shown no interest in hitting Western targets.
Intelligence officials say they have evidence that some Boko Haram members have trained in Niger and have made contact with al Qaeda's North African wing, which may explain the move.
Jonathan tightened security after the attack and armed soldiers patrolled Abuja, searching cars at roadblocks across the city, which lies in the middle of the country where the mostly-Christian south and largely-Muslim north meet.
Security experts say many of Boko Haram's attacks are done by disillusioned youths, in a region that has much higher illiteracy, poverty and unemployment rates than the south.
A security source on Saturday told Reuters he suspects there may also be a political dimension to its growing attacks, suggesting they are being co-opted by northern politicians angry about Jonathan, a Christian southerner, winning April's poll.
(Reporting by Felix Onuah; Writing by Tim Cocks; Editing by David Stamp and Karolina Tagaris)