LAGOS, Nigeria—Security officials here are concerned that an Islamic militant group believed responsible for a deadly suicide attack on the United Nations compound has splintered into two factions: one focused on local grievances and another that is seeking contacts with outside terror groups—including al Qaeda—and weighing fresh attacks.
On Sunday, a U.N. spokesman said the death toll from Friday's attack had risen to 23, and that 81 people were wounded. Of the 23, nine were U.N. staff, he said.
A Honda Accord packed with explosives was driven through the exit gate of the U.N. building and into the lobby, at which time it blew up and destroyed a large section of the building.
U.N. Deputy Secretary-General Asha-Rose Migiro and Nigerian President Goodluck Jonathan visited the bombing site over the weekend, and both vowed to continue fighting terrorism. "We condemn it in the strongest terms, but this act of terrorism will only rekindle our resolve to fight terrorism in all of its ramifications," Ms. Migiro said on Sunday.
Although the militant group, Boko Haram, has carried out a series of increasingly deadly attacks over the past year, it isn't known to have gone after a foreign target before. In the search to explain the shift, foreign and local security officials are coming to a share the view that the group has split into factions.
The radical splinter group is believed to have more than a dozen members trained to carry out suicide bombings, said an undercover Nigerian security official based in northern Nigeria. At least four other attacks are planned throughout Nigeria, he said, and may include additional foreign targets. The official couldn't provide more detail but said security officials were working to prevent the attacks.
A Western security official, based in the capital, Abuja, said the more radical faction "may have wanted to prove themselves" with Friday's attack. Part of the reason, he said, may have been to help establish more-concrete ties with terrorist groups outside Nigeria such as al Qaeda in the Islamic Maghreb.
"One faction vowed that they would not carry out attacks during the Ramadan period, and they've stood by their word," said the Nigerian security official, referring to the holy Muslim holiday now under way. "The other said they will continue, Ramadan or no Ramadan."
The less-extreme of the two factions appears focused on local grievances, such as non-Islamic practices that include Western-style education in schools and the existence of bars and clubs in the predominantly Muslim north. This wing of Boko Haram is also open to reconciliation talks with the Nigerian government, said Oronto Douglas, a senior adviser to President Jonathan. In the wake of Friday's attack, Mr. Douglas said his government is seeking "greater collaboration between security agencies across the globe." including invitations to the and others to assist with the probe of the attack.
On Saturday, U.S. Federal Bureau of Investigation agents visited the bombing site following the Nigerian government invitation, said a U.S. Embassy spokeswoman.
Boko Haram hasn't issued a statement claiming responsibility for the attack, nor has any other group.
But on Saturday, a man claiming to be a Boko Haram member took credit for the attack in a phone interview with The Wall Street Journal. The man, who identified himself as Abu Qaqa, said the group targeted the U.N. because it represents international bodies that support the Nigerian government. The group blames the Nigerian police for killing their leader in 2009 while he was in custody, and for carrying out other attacks on its members more recently.
A police spokesman couldn't be reached for comment on Sunday.
"If nobody touches us, we won't touch them," he said in the phone interview. "But if any group or country comes after us, we will go after them."
Mr. Qaqa said the group is receiving training outside Nigeria, but wouldn't elaborate and didn't discuss the existence of a more extreme Boko Haram faction. He said Boko Haram—which roughly translated means "Western education is sin"—supports other terror organizations operating in Africa. He declined to discuss possible links with al Qaeda, but officials say they believe some Boko Haram members may have received training outside Nigeria.
Mr. Qaqa also said most of the group's funding comes from robbing banks. Boko Haram is thought by authorities to be behind two bank robberies last week in northeastern Nigeria, during which a total of 12 people were killed.
In response to claims from Boko Haram taking responsibility for the attack, the U.N. spokesman said: "As far as we're concerned the claim has been made and it's been still being assessed. There had been general threats made [against the U.N.], but if there is a nonspecific threat, we can't stop [operations] because diseases don't stop."
The U.N. Development Program and Unicef are among the U.N. bodies working in Nigeria on poverty alleviation, education and health programs.
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