Tim Cocks / Reuters, file

Nigerian forces gather Monday in the Islamist stronghold of Maiduguri. Soldiers poured in this weeek before the military on Friday launched a major offensive against the insurgents.

MAIDUGURI, Nigeria -- Nigerian forces used jets and attack helicopters to bombard Islamist militant camps in the northeast on Friday, in their biggest military offensive since Boko Haram launched an uprising in 2009.

"A number of insurgents have been killed," the defense headquarters spokesman said, including at the Sambisa game reserve in Borno state, the epicenter of the insurgency.

"It is not just Sambisa. Every camp is under attack. But we have not done the mopping-up operations on the ground to determine the numbers killed," Brig. Gen. Chris Olukolade said by telephone. Another military source, who declined to be named, said at least 30 insurgents had been killed.

Nigerian forces are trying to regain territory controlled by increasingly well-armed Boko Haram Islamist insurgents in their northeastern stronghold states of Borno, Yobe and Adamawa, put under a state of emergency by President Goodluck Jonathan on Wednesday.

More troops arrived in the Borno state capital, Maiduguri, on Friday, witnesses said.

"I saw more than 20 trucks loaded with soldiers fully kitted for battle towards Marte. I wish them luck in ending this BH (Boko Haram) madness," resident Ahmed Ibrahim said by telephone.

Beyond the region covered by the state of emergency, gunmen stormed a police station and a bank, the army said, a sign the offensive could provoke violence by smaller militant cells across the north.

Boko Haram, other Islamist militant groups such as al-Qaeda-linked Ansaru and associated criminal gangs have become the biggest threat to stability in Africa's top oil-producing nation.

Thousands have been killed since Boko Haram launched an uprising almost four years ago in an effort to create an Islamic state in a country of about 170 million split roughly equally between Christians, who are the majority in the south, and Muslims, who predominate in the north.

Violence has mostly happened far from the commercial hub, Lagos, or political capital, Abuja, and hundreds of miles away from oilfields in the southeast.

Military jets, helicopter gunships and thousands of troops are involved in the current offensive, which may answer some critics who accuse Jonathan, a southern Christian, of underestimating the severity of the crisis in the Muslim north.

Rights groups are concerned the state of emergency will lead to more abuses they have document by Nigerian forces.

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Reinnier Kaze / AFP - Getty Images

(From left) Former French hostages Tanguy Moulin-Fournier, his wife Albane and his brother Cyril pose at the French embassy in Yaounde on Friday. The family of seven were kidnapped in Cameroon in February by an Islamist movement from neighboring Nigeria.

YAOUNDE, Cameroon -- A French family of seven, including four children, have been released in Cameroon following secret talks, France said on Friday, ending two months of captivity in the hands of Nigerian Islamist militants.

Armed men on motorcycles snatched the family on February 19 while they were on holiday near the Waza national park in north Cameroon, some 6 miles from the Nigerian border.

"I spoke to the father this morning ... He told me how happy and relieved he was," French President Francois Hollande told a news conference in Paris on Friday. "This is an immense relief. This will redouble our determination to free the hostages who remain."

Eight French hostages remain held by al Qaeda-linked Islamist militant groups in the Sahel region.

Hollande said there had been contacts over the last few weeks to discreetly free the family under French terms and denied any ransom was paid.

"France has not changed its position, which is not to pay ransoms," he said.

The father of the kidnapped family, Tanguy Moulin-Fournier, worked in Cameroon for French utility firm GDF Suez. He was kidnapped with his wife, two daughters and two sons, and his brother, who was visiting them on holiday.

"We are very happy to be released. I want to thank (Cameroon) President Paul Biya for making all the effort to ensure our release," his tired-looking wife, Albane Moulin-Fournier, said on Cameroon television, holding her smallest child.

Both adult males of the family had thick beards while the children looked drawn, and wore flip-flops, knee-length trousers and tee-shirts.

Ferdinand Ngoh Ngoh, secretary-general of Cameroon's presidency, said all family members were well.

State television showed the family descending from a plane where they were greeted on the tarmac by the French ambassador who took them to the embassy in the capital Yaounde.

French Foreign Minister Laurent Fabius was due to meet them there, a French official said, and they would be repatriated to France as soon as possible.

The release of the hostages is a rare piece of good news for Hollande's government, which is struggling to cut unemployment and has been hit by a tax fraud scandal which has forced its budget minister to resign.

Mostly Muslim northern Cameroon is considered an area within the operational sphere of Islamist militants including Boko Haram, Nigeria's biggest security threat.

Gunmen claiming to be from Boko Haram released videos of the family in March, threatening to kill them unless Nigeria and Cameroon released Muslim militants held in detention.

Cameroon denied it was holding any militants and it was unclear if any of the group's demands had been met.

Additional reporting by John Irish and Brian Love in Paris.

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KANO, Nigeria -- Gunmen on motorbikes shot dead nine health workers who were administering polio vaccinations in two separate attacks in Nigeria's main northern city of Kano Friday, police said.

No one claimed responsibility but Islamist militant group Boko Haram -- a sect which has condemned the use of Western medicine -- has been blamed for carrying out a spate of assaults on security forces in the city in recent weeks.

It is the second time this year that polio workers have come under attack by Islamist militants, after gunmen killed aid workers tackling the disease in Pakistan last month.

Some influential Muslim leaders in Kano openly oppose polio vaccination, saying it is a conspiracy against Muslim children.

The attacks will hit efforts by global health organizations to clear Nigeria's mostly-Muslim north of polio; a virus that can cause irreversible paralysis within hours of infection.

"Gunmen on bikes opened fire on a health center in the Hotoro district killing seven, while an attack on Zaria Road area of the city claimed two lives," said police spokesman Magaji Musa.

"They were working for the state government giving out polio vaccinations at the time of the attack," Musa added.

Kano government banned motorbikes from carrying passengers last month after the Emir of Kano, one of the country's most prominent leaders, was nearly killed when gunmen attacked his convoy, killing four of his aides.

Militants pose serious threat
Boko Haram killed hundreds last year as part of its campaign to impose Islamic law, or sharia, on a country of 160 million, split roughly equally between Christians and Muslims.

The group is seen as the most serious threat to the stability of Africa's top energy producer, and Western governments fear the country could become a base for operations of al-Qaida-linked Islamist groups in the Sahara.

President Goodluck Jonathan has highlighted links between Boko Haram and Saharan Islamists and said that relationship justified his decision to join efforts by French and West African forces to fight militants in Mali last month.

In 2003, northern Nigeria's Muslim leaders opposed polio vaccinations, saying they could cause infertility and AIDS.

Their campaign against the treatments was blamed for a resurgence of the disease in parts of Nigeria and other African countries previously declared polio-free.

Polio, a virus that attacks the nervous system, crippled thousands of people every year in rich nations until the 1950s. As a result of vaccination, it is now only endemic in three countries -- Afghanistan, Nigeria and Pakistan.

According to the Global Polio Eradication Initiative, there were 121 new cases of polio in Nigeria last year, compared to 58 in Pakistan and 37 in Afghanistan.

"This is certainly a setback for polio eradication in Nigeria, but not a stop," said Oyewale Tomori, a campaigner for polio eradication in Nigeria. "The best we can do is to work harder and see the end of polio ... so their loss will not end as a useless sacrifice."

At least 16 health workers taking part in polio vaccination drives were killed in attacks in Pakistan in December and January.

Local Taliban militants said they did not carry out those attacks although its leaders have repeatedly denounced the vaccination program as a plot to sterilize people or spy on Muslims.

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MAIDUGURI, Nigeria -- Nigeria's military killed 13 members of the Islamist militant group Boko Haram and lost one soldier on Tuesday in a gunbattle in Maiduguri, the group's northeastern stronghold, the army said.

Boko Haram, which is loosely based on the Afghan Taliban, killed hundreds last year in a campaign to impose Shariah, or Islamic law, in Nigeria, a country of more than 160 million split roughly equally between Christians and Muslims.

On Dec. 28, five people, including a police officer, were killed by gunmen believed to be Boko Haram members, police said. At least 32 people have now died in the northeast in the last week in violence presumed to be linked to Islamist militancy, the biggest threat to stability in Africa's main oil exporter. 

"One soldier was killed by Boko Haram while the JTF killed 13 Boko Haram," Sagir Musa, spokesman for the military Joint Task Force, said on Tuesday.

Nigeria church attack kills 19

The military in the northeast have in the past played down their own casualties in fighting with Boko Haram.

Musa said that members of the sect had detonated a bomb at a JTF checkpoints in Maiduguri, and that all the deaths had occurred in the ensuing gunbattle.

Christians told to leave northern Nigeria or be attacked

Maiduguri, a remote, dusty town close to the borders of Chad and Niger, has been a hotbed of violence, directed mostly at the security forces, since Boko Haram took up arms in 2009.

Boko Haram's insurgency intensified after Goodluck Jonathan, a southern Christian, was elected president in April 2011.

Gunmen kill at least 25 at Nigeria college residence

Jonathan has been unable to stop the rebellion despite waves of military offensives in the northeast and other parts of northern and central Nigeria where Boko Haram has a strong presence.

Western governments are increasingly concerned about Islamists in northern Nigeria linking up with outside groups, including al-Qaida's North African wing.

More Nigeria coverage from NBC News

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KADUNA, Nigeria -- Gunmen shot dead at least 25 students in an attack on their college residence in northeast Nigeria, authorities said.

The overnight attack took place at the Federal Polytechnic Mubi in remote Adamawa state late on Monday, the head of the information department at the college told Reuters.

"The killers went from room to room, slaughtering them one by one," said witness Mohammed Awal, who was not harmed in the attack. Some were shot, others killed with machetes, he said.

Citing local residents, Voice of America reported that the victims were "individually questioned before being attacked."

Political feud?
Adamawa state, like much of the north, has been targeted by Islamist insurgents, but police were also investigating whether the killings might have been motivated by a political feud inside the college.

"We learned that when they came for the attack, they called out the names of some of the victims and killed them as they came out. Some they left alone, which gives us a clue that this was the work of insiders," Adamawa police spokesman Mohammed Ibrahim said. He put the toll confirmed by police at 25.

He said the student halls had been raided by police last week as part of a sweep against Boko Haram militants. During the raid, police recovered weapons including a rocket-propelled grenade, dozens of homemade bombs, knives and automatic assault rifles. He added that it could not be ruled out that Boko Haram militants who had infiltrated the students were behind it.

A security source and several witnesses put the overall death toll from the attack at 40.

Voice of America added: 

Daniel Babayi, the executive secretary of the Northern States Christian Association of Nigeria, says he believes the killings were a reprisal attack after 156 people were arrested and accused of being members of the Islamist militant group known as Boko Haram late last month.

The Boko Haram Islamist sect, which usually targets politicians or security forces, has also attacked students in the past and has cells in Adamawa. Security sources believe it has infiltrated several institutions, including colleges.

More international stories from NBC News

But police were also investigating the possibility that the killings were related to a dispute between rival political groups at the college over a student union election on Sunday, in a part of Nigeria that is awash with weapons.

Colleges across the country are sometimes plagued by armed gangs and vigilante groups.

"The crisis in Mubi is suspected to have been fueled by campus politics after the election ... the ones who were disgruntled might have ... (carried out) the attack," said National Emergency Management Agency spokesman Yushua Shuaib.

More Nigeria coverage from NBC News

Boko Haram is widely considered to be the biggest security threat in Nigeria, Africa's biggest oil exporter. It has been blamed for more than 1,000 deaths since its insurgency -- which aims to carve out an Islamic state out of northern Nigeria -- intensified in 2010.

Boko Haram's purported leader released a video on Monday in which he vowed to continue fighting and said no peace talks with the government could happen while military raids against sect members continued.

Reuters contributed to this report.

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Gunmen killed 19 people when they fired on worshipers at a church in Nigeria's central Kogi state during a Monday evening service, police said on Tuesday, the BBC reported.

"A group of three unidentified gunmen stormed the Deeper Life Church in Okene and opened fire on them, killing 16," Simeon Ille, spokesman for the Kogi state police, told Reuters by phone. The BBC reported that 19 people had been killed.

According to the BBC, the pastor was among those killed. The gunmen fired Kalashnikov assault rifles.

A witness, who asked not to be identified for fear of being targeted, said around 10 gunmen blocked off the exits to the church before shooting the trapped people inside.

Ille said security forces last month prevented a suspected suicide bomber from detonating an explosive at a different church in Okene, a town around 140 miles south of the capital Abuja. The suspected would-be bomber fled, he said.

Islamist sect Boko Haram has attacked several churches this year in Nigeria but Monday's attack was farther south than the group's usual targets.

In February, Boko Haram claimed a prison break in Kogi state when 119 prisoners were freed. The sect has carried out jail raids before and one of its key demands is the release of its imprisoned members.

The group's strikes are increasingly spreading across Nigeria, Africa's biggest oil producer. Cities across the north and in the capital Abuja have been hit in recent months by suicide bombers, never seen before last year in Nigeria.

The country's two-million-barrel-per-day crude oil export business in the southern coastal region has not been affected by the sect's violence.

The sect has killed hundreds this year in its insurgency against President Goodluck Jonathan's government. It wants to have an Islamic state inside Nigeria, a country of more than 160 million split roughly equally between Christians and Muslims.

The group, which is loosely based on Afghanistan's Taliban, usually target authority figures and places of worship to settle scores with people they say harmed their members.

Reuters contributed to this report.

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KANO, Nigeria - Gunmen killed at least 15 people and wounded many more in an attack on a university theater being used by Christian worshippers in Nigeria's northern city of Kano on Sunday, a witness said.

It was the latest in a spate of attacks on churches and on Christian holidays in the north of the country, which Nigerian authorities and diplomats believe are part of an attempt to stoke a religious conflict.

Security sources said there was sporadic gunfire in other parts of the city which they believe was from attackers who were fleeing from the army at the university. "I counted at least 15 dead bodies. I think they were being taken to the Amino Kano teaching hospital," the witness, who did not wish to be identified, said, adding that he saw many more people being treated for injuries.

A security source said at least 15 people were dead and a source at the hospital told Reuters by phone that he had seen 10-15 dead bodies brought in with gunshot wounds.

There was no immediate claim of responsibility.  

Radical Islamist sect Boko Haram, which wants to carve out an Islamic state in northern Nigeria, has killed hundreds in bomb and gun attacks this year. It mainly targets police and authority figures but has also attacked churches.

At least four killed as two bombs hit Nigeria newspaper offices

The army said it had secured the area but could not say how many people had been killed.

"The attack took place in one of the lecture theatres used as a place of worship by Christians. For sure there are casualties but I can't say how many," Ikedichi Iweha, an army spokesman, told Reuters.

"The elements came, used explosives and guns to attack them. We have repelled them and cordoned off the area," Iweha said.

Red Cross officials said they were trying to get access to the area but there were no details on casualties.

Bomb explosions
"For over 30 minutes a series of bomb explosions and gun shots took over the old campus, around the academic blocks," said Mohammed Suleiman, a history lecturer at the Bayero University.

"It started at about 0930 (1:30 a.m. ET) this morning ... our school security men had to run for their dear lives. You can see smoke all over," Suleiman said.

Clashes between Boko Haram gunmen and security forces have flared up several times in Kano since the sect killed 186 people in January, its deadliest attack so far.

On Easter Sunday, 36 people were killed when a suspected member of Boko Haram attempted to force a car packed with explosives into a church compound during a service in the northern town of Kaduna.

Thousands of Nigerians protest fuel prices, as government fears 'anarchy'

After being stopped by security he turned back and the bomb exploded by a large group of motorbike taxi riders.

Boko Haram set off a series of bombs across Nigeria on Christmas Day last year, including one at a church outside the capital Abuja that killed at least 37 people.

Africa's most populous nation of more than 160 million is split roughly equally between a largely Christian south and a mostly Muslim north.

Suicide car bombers targeted the offices of Nigerian newspaper This Day in the capital Abuja and in Kaduna last week, killing at least four people in coordinated strikes.

This Day is based in southern Nigeria and is broadly supportive of President Goodluck Jonathan's government - the main target of Boko Haram's insurgency.

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The United States has warned its citizens living in Nigeria that Islamist sect Boko Haram is planning attacks on the capital Abuja, including major hotels there. 

"The U.S. Embassy has received information that Boko Haram may be planning attacks in Abuja, Nigeria, including against hotels frequently visited by Westerners," an emergency message on its website said. 

Boko Haram has killed hundreds in gun and bomb attacks this year. Its strikes usually target police, authority figures and churches in the mostly Muslim north, although there have been a handful of deadly strikes in and around the capital. 

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