Boko Haram, Nigeria's homegrown Islamic extremist group, is increasing the ferocity and tempo of its attacks, destabilizing Africa's most populous nation as it prepares for elections.

Girls as young as 10 are being used as suicide bombers. There have been daring attacks on military barracks in Nigeria and Cameroon. The group, which wants to impose Shariah across the country and is increasing its territory under a self-proclaimed Islamic caliphate, recently massacred hundreds of civilians, with death toll estimates ranging up to 2,000.

President Goodluck Jonathan, the front-runner in the Feb. 14 presidential and legislative elections, launched his campaign last week with no reference to the seizure of a key military base at Baga, near the border of Cameroon and Chad. As soldiers fled the base on Jan. 3, Boko Haram went on a killing spree, reportedly drowning many in Lake Chad. Amnesty International called it the deadliest massacre in Boko Haram's 5-year insurgency.

Survivors have described hundreds of fighters riding into town in a column led by an armored personnel carrier stolen from the military, on the backs of pickup trucks and on motorcycles, firing rocket-propelled grenades and assault rifles and hurling homemade bombs that set buildings ablaze.

A military officer said that more than 10 days later, Baga remains under the control of Boko Haram.

"We have not heard any order deploying soldiers to return to Baga for now," he said. He spoke on condition of anonymity because he feared being punished by his superiors for talking to the press. "As a matter of fact, most of the soldiers that managed to escape from Baga had redeployed back to their mother stations of deployment."

The marginalized part of the country is semi-arid desert that turns to lush forest around Lake Chad and is home to traders, subsistence farmers, herdsmen and fishermen. It includes a couple of the biggest cattle markets on the continent.

Since August, when the insurgents declared they were recreating an ancient Islamic caliphate that included parts of Cameroon, Chad and Niger, they have seized or consolidated control of more than 10 percent of Nigerian territory, mostly in the state of Borno where the group was created. In Borno, Boko Haram holds 14 of the 27 local government areas including all the border crossings into Niger, Chad and Cameroon.

This week, hundreds of Boko Haram fighters attacked a Cameroonian military camp near the border, but, according to Cameroonian officials, they bit off more than they could chew. Cameroon's government said Tuesday that its military killed 143 militants with only one Cameroonian soldier killed.

Boko Haram also holds small parts of Nigeria's Adamawa and Yobe states. While most attacks occur in the northeast, leaving many Nigerians remote and uncaring about the conflict, hundreds were killed last year in car bomb attacks in Abuja, Nigeria's capital, and in Jos, both in central Nigeria.

Analysts say Boko Haram fighters numbered no more than 4,000 or 5,000 about 18 months ago when they began abducting hundreds of mainly young females and males. The group also has been recruiting fighters for pay in neighboring countries.

While there is little likelihood of Boko Haram overrunning Nigeria, many worry that the group's hostility to democracy will increase attacks around the elections. Nigerian troops have been unable to snuff out the insurgency despite a pledge by top commander last year to do so in a three-month span.

Boko Haram attracted international attention when it seized some 276 schoolgirls from a boarding school in April last year. Dozens escaped on their own but the failure of Nigeria's government and its once-powerful military to rescue 219 who remain missing has brought condemnation and puzzlement.

Nigeria's military budget amounts to between $5 billion and $6 billion a year, yet soldiers are reportedly being sent into battle with just 30 bullets, former U.S. Ambassador John Campbell to Nigeria told The Associated Press.  Several generals last year were found guilty by a court-martial of delivering arms and information to Boko Haram. Soldiers say they are demoralized because Boko Haram outnumbers and outguns them where they're deployed in hostile territory without even food rations and because officers steal part of their salaries. Some of the troops who are supposed to be rotated every six months have been in the war zone for more than two years.

Campbell, now a member of the Council on Foreign Relations, said that Nigeria's military, once considered the single national institution that would prevent the country from breaking apart, is riven by tribal and religious cleavages.

Nigerian officials insist that voting will be carried out in the northeast next month, but it will be a challenge if not impossible to conduct the polling in an area where some 1.6 million people have been driven from their homes and in places where even government soldiers don't dare to tread.