Attackers killed eight people in a village in northern Nigeria's embattled Borno state, with at least some of the victims' throats slit, officials and residents said Monday.

The military spokesman in the area, Lt. Col. Sagir Musa, confirmed that an attack had occurred Sunday in the village of Gajiganna, but declined to comment on the manner in which people were killed, saying only that "lives were lost."

Nigerian President Goodluck Jonathan said Wednesday that Islamist extremist group Boko Haram would pose a threat to other African nations if not contained, while also pledging support for Mali.

Jonathan, speaking in an interview with CNN, however did not offer details while denying the Boko Haram insurgency was spurred by deep poverty in Nigeria's mainly Muslim north and refuting widespread reports of major military abuses.

Attackers beheaded five people after storming into their homes on Wednesday in the Nigerian city of Maiduguri, the base of an insurgency by Islamist extremist group Boko Haram, residents said.

"I saw the five decapitated bodies before they were taken away by soldiers from the (military task force)," one resident told AFP of the attack in the northeastern city.

The death toll in a gun attack on the convoy of Emir of Kano, an influential Nigerian Muslim figure, has risen to five, the police said, as the monarch and his injured sons flew out of the country on Sunday.

"The interim chairman of Kura local government and his driver were also killed by some gunmen who pursued them from the scene of the attack" on Emir Ado Bayero, Kano police spokesman Magaji Majia told Agence France Presse.

Police in Nigeria have found at least 15 unidentified corpses floating on a river in southeast Anambra state, officials said Sunday, while local media said the number of bodies could be much higher.

"I don't know the exact number of bodies but I have seen at least 15 corpses floating on the river," Anambra police commissioner Bala Nasarawa said in a television interview after visiting the scene.

Two soldiers were killed and five others injured Saturday in an explosion in Okene city in Nigeria's central Kogi state, an army spokesman said, adding that they were part of the contingent set to be deployed to Mali.

"We lost two soldiers while five others were wounded when the IED (improvised explosive device) planted on their route went off and hit their convoy," Major General Bola Koleoso told Agence France Presse.

An explosion and fire hit an area of Nigeria's main seaport on Wednesday in the country's largest city of Lagos, shaking buildings in the area and wounding at least four people, an official said.

Details were still emerging of the incident in the Apapa area of Lagos, but initial information indicated there had been an explosion on a ship and fire broke out afterward in an area where fuel was being unloaded at a jetty.

Pirates have freed three Italian sailors they abducted from a ship off Nigeria last month, the foreign ministry said in a statement Wednesday.

"Our three sailors are free and will soon return to Italy," Foreign Minister Giulio Terzi said in a statement, while the ministry said the Italians would be flown back into the country later Wednesday.

Nigeria's navy has transferred for prosecution 15 Russian sailors detained since October for allegedly transporting illegal arms, a navy spokesman said Tuesday.

"The police have taken over the custody of the 15 Russians because the navy does not have the power to prosecute them," Lieutenant Commander Jerry Omodara of the Western Naval Command in Lagos, told Agence France Presse.

Malian soldiers fired warning shots at Islamist fighters overnight amid fears that they are planning to advance on the government-controlled south of the impoverished country, a military source said Tuesday.

The fighters retreated after the firing near the town of Kona in the central Mopti region, the source told Agence France Presse.