| MAIDUGURI, Nigeria
MAIDUGURI, Nigeria (Reuters)- An Islamist sect claimed responsibility for a bomb attack on the U.N. headquarters in Nigeria that killed 23 people, demanding the release of prisoners and an end to a security crackdown to prevent further bombings.
Boko Haram, which has been behind almost daily shootings and attacks with homemade bombs in the remote northeast, was the prime suspect in Friday's car bombing of the United Nations' Abuja office -- one of deadliest attacks on the world body in its history.
"We are responsible for the bomb attack carried out on the U.N. building in Abuja," a Boko Haram spokesman calling himself Abu Kakah told local journalists in a statement over the weekend.
The bomb gutted a lower floor, smashed almost all of the building's windows and wounded 76 people, U.N. officials said. The driver was killed in what could be Nigeria's first suicide bomb attack.
President Goodluck Jonathan has condemned the strike but refused to be drawn on who could have carried it out. Security services in Abuja also declined on Monday to comment on who they believe was behind the bombing.
The spokesman also claimed responsibility for other attacks in northeastern Nigeria.
"(We did) the bombings at Gombi, Bauchi as well as the attempt at the police HQ in Maiduguri. (This was punishment) for the humiliating treatment meted out to our members by security agencies in various parts of the country," he said.
Boko Haram's usual representative, Abu Zaid, is out of the country, but local journalists who received the statement said he had contacted them to make Kakah spokesman in the interim.
"The government must release all our members detained in various prisons across the country unconditionally before we accept dialogue with the government. The identity of the Abuja U.N. building bomber will be revealed to the public soon."
The group -- whose name means "Western education is sinful,"
is loosely knit, with many claiming to speak on its behalf, which makes verifying responsibility difficult.
However, the U.N. bombing marks an increase in the sophistication of its attacks and an escalation from local to international targets.
This has led some analysts to suggest the group is developing global ambitions and may have linked up with al Qaeda's North African wing, already operating in Nigeria's neighbor Niger.
But Kakah's statement suggested local concerns were still at play. "I am using this opportunity to warn the security agencies in (the northern state of) Kano to stop persecuting our members otherwise they shall be our next target," he said.
Amnesty International has said brutalization by security forces, unlawful arrests, killings and disappearances have been the operating practice in Maiduguri, further radicalizing local residents against authorities.
Jonathan last month set up a seven-man committee led by Borno civil servant Usman Gaji Galtimari to investigate the causes of unrest in the northeast, where Boko Haram is based. It is due to submit its report this week.
"Boko Haram has no confidence in the Presidential Committee set up to dialogue as nobody has ever contacted us for any dialogue. That whole affair is just a huge joke meant to deceive us," Kakah said.
(Writing by Tim Cocks; Editing by Joe Brock and David Stamp)