Boko Haram loosely translates from the Hausa language of northern Nigeria as "Western education is sinful", though more accurately as a prohibition on being fake or inauthentic.

Either way, the Islamist insurgents have made a point of targeting schools - 254 have been destroyed, emergency officials said last week - and Boko Haram's growing list of atrocities includes the kidnapping in April of nearly 220 school girls from villages where the Christians are in the majority.

"Even if you don't do anything to us, we will kill you," was the chilling warning in August from the group's commander, Abubakar Shekau, a man with a $US7 million bounty on his head. Boko Haram has been branded the Nigerian Taliban and regularly issues blood-soaked condemnations of the local government and the West.

Shekau, who has been mistakenly declared dead several times in battles only to rise again, claims to desire a land governed by Sharia and reclaim a 19th century caliphate in the region that fell to British colonialism. Women have been stoned to death for adultery and abuses are commonplace.

But close observers warn Boko Haram fighters are far from united. Different factions have at times negotiated ceasefires with the Nigerian army, or taken up arms in neighbouring countries of Cameroon, Chad and Niger, bringing unwelcome extra pressure on the militants.

Cameroon claimed to have killed more than 140 Boko Haram fighters on Tuesday after they sought to overrun a military base.

How much of a threat does Boko Haram pose?

Severe, but more as agents of chaos than a truly alternative regime.

Bombing, looting, raping, the insurgents keep leaving corpses in their wake. Nigeria's army has disputed the claims Boko Haram massacred 2000 people around the border town of Baga, saying the number of dead is closer to 150. But there is no denying Boko Haram has become ever more brazen in its rampage.

Nigerian authorities claim more than 800,000 people have been displaced by more than five years of fighting that threatens to cripple Africa's most populated country and largest economy. The Islamists have proved too strong for Nigeria's ill-equipped and often corrupt army to stamp out - and now loom menacing over the country's February 14 presidential elections.

Suicide bombings are increasingly common. Girls as young as 10 and 15 are thought to have killed themselves and more than two dozen others in explosive attacks in the last fortnight.

Is Boko Haram a threat to the West?

The US government has accused Boko Haram of trading weapons and training with al-Qaeda-affiliated fighters in northern Africa and Somalia. Australia has officially designated the group as a terrorist organisation.

But Boko Haram's attacks on the West has so far been confined to a few scattered targets inside Nigeria and kidnapping a handful of foreigners. The condemnations of the West have so far been most for propaganda, to motivate fighters. Boko Haram also exploits resentment in the north over poor investment and few jobs.

Nigeria's government has complained it has not received sufficient Western aid and intelligence support to tackle the insurgents.

What has Nigeria's government done?

"This terrorism cannot last forever," President Goodluck Jonathan said on the campaign trail last week. "If my administration is re-elected, terror will be minimal." His promise seemed a hollow one, if past actions are anything to go by.

"This rag-tag gang outwits our supposedly well-trained and well-armed troops," complained the New Year editorial in Desert Herald, a local paper that has made reporting on Boko Haram a priority.

One retired general condemned the army for imposing the death sentence on 54 soldiers accused of mutiny, after they refused to fight unless supplied with better weapons. The government's response has been to raid media organisations that have published critical stories.

Even so, Jonathan has been severely criticised for reacting too slowly to gains by Boko Haram and failing to rescue the kidnapped school girls.

His main rival in the presidential race, former general Muhammadu Buhari, has branded Boko Haram "mindless bigots masquerading as Muslims". Buhari, from the roughly 45 per cent of the population who are Muslims and a former head of state, has dismissed criticism he was responsible for running down spending on the military.

Where are the school girls?

The global online campaign #BringBackOurGirls failed miserably. Boko Haram claimed in October the girls have converted to Islam and married fighters.

Human rights activists fear their fate to be far worse, believing the girls have been forced to become sex slaves - either for Boko Haram or trafficked to other countries, as far away as Sudan and Libya.

According to some counts, a lucky 40 of the kidnapped girls have escaped.