Nigerian security forces searched for a kidnapped German engineer on Friday as the Boko Haram Islamist group threatened new attacks in Africa's most populous nation and top oil producer.
In an audio recording posted on YouTube, Abubakar Shekau said he ordered the coordinated attacks that killed at least 185 people in Kano on January 20 and vowed that the group would strike again.
"We were responsible," said Shekau of the January 20 assaults, the deadliest ever attributed to the shadowy group.
"I ordered it and I will give that order again and again. God gave us victory," he said.
The authenticity of the Hausa language message, which played above a picture of Shekau with a Kalashnikov set in the background could not be independently verified.
But the photo appeared to match with previous ones said to be of Shekau and the voice sounded similar to earlier recordings.
"We attacked the security formations because our members were arrested and tortured. Our women and children have also been arrested," he said.
"They should know that they also have wives and children. We can also abduct them. It is not beyond our powers."
Boko Haram has previously said that it wants to create an Islamic state in Nigeria's deeply-impoverished mainly Muslim north, charging the government with harassing Muslims and raiding Islamic schools.
"Soldiers raided an Islamic seminary in (the northern city) of Maiduguri and desecrated the Koran. They should bear in mind that they also have primary and secondary schools and universities, and we can also attack them."
But after a meeting with governors from 19 northern Nigerian states early Friday, Nigeria's Vice President Namadi Sambo denied that religious tensions were fuelling the Boko Haram menace in the country whose population is roughly divided between a mainly Muslim north and a mainly Christian south.
"It is very clear that there is no religious problem, religious fighting in northern Nigeria," Sambo told journalists.
Shekau was seen as Boko Haram's second-in-command at the time of a 2009 uprising put down by a brutal military assault, after which the group went dormant for about a year before re-emerging in 2010 with increasingly sophisticated attacks.
There has been intense speculation about Boko Haram's links to foreign Islamist groups, specifically Al-Qaeda's north Africa franchise, known as Al-Qaeda in the Islamic Maghreb (AQIM).
Speaking to AFP a western diplomat downplayed the strength of those ties.
"I think there's evidence of contact (with foreign groups), but in terms of operationally linking up with AQIM or extremist groups elsewhere, we don't see Boko Haram as an Al
Qaeda franchise," said the diplomat who requested anonymity.
In Kano, hit by a fresh blast on Thursday after armed men stormed a police station two days earlier, gunmen kidnapped a German engineer working with a Nigerian construction company Dantata and Sawoe.
Edgar Raupach was seized by men who "came and handcuffed him and put him in the boot and zoomed away," said Kano police spokesman Magaji Majia.
Regional police immediately sent out an alert.
"All the major highways were blocked and even the neighbouring states were equally alerted," he said on Thursday.
An official from the German embassy in Nigeria said its staff were trying to verify the police account.
The kidnapping of foreigners is rare in northern Nigeria and there were no immediate indications that Boko Haram was linked to the abduction.
In a related context, The Libyan civil war may have given militant groups in Africa's Sahel region like Boko Haram and al Qaeda access to large weapons caches, according to a U.N. report released on Thursday.
The report on the impact of the Libyan civil war on countries of the Sahel region that straddle the Sahara - including Nigeria, Niger and Chad - also says some national authorities believe the Islamist sect Boko Haram has increasing links to al Qaeda's North African wing. Boko Haram killed more than 500 people last year and more than 250 this year in Nigeria.
The U.N. Security Council met to discuss the report, which was prepared by a U.N. assessment team that met with officials from countries in the region. The discussion highlighted the deep divisions between Western powers and Russia over NATO's intervention in the North African oil-producing state.
"The governments of the countries visited indicated that, in spite of efforts to control their borders, large quantities of weapons and ammunition from Libyan stockpiles were smuggled into the Sahel region," the report said.
Such weapons include "rocket-propelled grenades, machine guns with anti-aircraft visors, automatic rifles, ammunition, grenades, explosives (Semtex), and light anti-aircraft artillery (light calibre bi-tubes) mounted on vehicles," it said.
More advanced weapons such as surface-to-air-missiles and man-portable air defense systems, known as MANPADS, also may have reached groups in the region, the report said.
U.N. special envoy to Libya Ian Martin, however, has told the Security Council that Libya's missing stocks of MANPADS have largely remained inside the country.
The report said some countries believe weapons have been smuggled into the Sahel by former fighters in Libya - Libyan army regulars and mercenaries who fought on behalf of former leader Muammar Gaddafi, who was ousted and killed by rebels.
Some of the countries told the assessment team that they had registered an increase in arms trade across West Africa.
"Some of the weapons may be hidden in the desert and could be sold to terrorist groups like al Qaeda in the Islamic Maghreb, Boko Haram or other criminal organizations," the U.N. report said.
'UNCONTROLLED SPREAD OF WEAPONS'
Lynn Pascoe, U.N. under-secretary-general for political affairs, told the Security Council that the new Libyan government insists many of the problems related to weapons and the Sahel originated when Gaddafi was still in power.
"Some of the problems are directly related to the fall of the Gaddafi regime in Libya but the nation's interlocutors emphasize that most of the problems are long-standing ones," he said.
British, French and U.S. envoys echoed the Libyan view that the problems existed long before the civil war.
Russia, which has criticized the toppling of Gaddafi and accused NATO of using a U.N. mandate to protect civilians in Libya as a springboard for regime change, said the U.N. report highlighted problems unleashed by NATO's intervention in Libya.
Russian envoy Alexander Pankin said the U.N. report confirmed that the "real consequences of the Libyan crisis, the real scope of which is only beginning to come to light, are a serious threat to security and stability in the entire region."
He said Moscow was especially concerned about "the uncontrolled spread of weapons in Libya and beyond its border."
The U.N. report said Nigeria was not the only country worried about the activities of Boko Haram. It said the group also was in Niger, adding that some governments believed Boko Haram members from Nigeria and Chad had received training at al Qaeda training camps in Mali in 2011.
"Although Boko Haram has concentrated its terrorist acts inside Nigeria, seven of its members were arrested while transiting through the Niger to Mali," it said, adding that they possessed documents about explosives manufacturing, propaganda leaflets and contact details for known al Qaeda members.
Links between al Qaeda and Boko Haram have become "a growing source of concern for the countries of the region," it said.