Here’s what we know so far about Boko Haram’s latest attack in Nigeria

JOHANNESBURG, South Africa — We have but glimpses of the horror in northeastern Nigeria, scant details of Boko Haram's latest brutal assaults on remote towns and villages.

Journalists are unable to work freely in the region. Information mostly comes from telephone calls to local officials, and interviews with residents who have fled the violence.

What seems clear is that the crisis has intensified ahead of Nigerian general elections next month.

Boko Haram has for the past five years waged insurgency in northern Nigeria, bombing big cities and razing villages as it seeks to establish an Islamic caliphate. In the latest barbaric attacks, the group's fighters laid siege to the town of Baga, in Borno state, after overrunning a military base there Saturday.

The base is the headquarters of a multinational task force, comprised of troops from Nigeria along with neighboring Niger and Chad. With the capture of the base, all three of Borno state's borders with Niger, Chad and Cameroon are now under Boko Haram's control — a strategic position from which to launch further onslaughts.

After taking the base, the insurgents next turned their attention to the civilian population in Baga and surrounding towns and villages.

Residents told of Boko Haram fighters torching homes in Baga and shooting wildly, including at women and children, in attacks that began Tuesday night and continued Wednesday.

Many residents of the fishing community fled across Lake Chad, some reportedly drowning along the way, while others escaped to Maiduguri, the state capital.

The UN's refugee agency said Friday that 7,300 people had arrived from Nigeria in western Chad in the last 10 days, including 1,000 people stranded on an island in Lake Chad.

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Survivors described seeing almost the entire town of Baga on fire, and bodies strewn in the streets.

Reports of the number of people killed have varied significantly. On Friday, Amnesty International said that the Baga attack may have been the "deadliest in Boko Haram's history."

"If reports that the town was largely razed to the ground and that hundreds or even as many as two thousand civilians were killed are true, this marks a disturbing and bloody escalation of Boko Haram’s ongoing onslaught against the civilian population,” Nigeria researcher for Amnesty Daniel Eyre said in a statement.

Musa Alhaji Buka, a local government official, told the BBC that 2,000 people were feared dead in the Baga attack. Other estimates range from dozens to hundreds killed.

According to the US-based Council on Foreign Relations, Boko Haram, whose name means "Western education is a sin," killed more than 10,000 people last year.

The militant group is believed to have seized more than two dozen towns in Nigeria's northeast in just the last six months. Borno state, hardest hit by the insurgency, is now said to be 70 percent under Boko Haram's control.

President Goodluck Jonathan is under mounting criticism for failing to tackle the crisis, and many Nigerians are wondering how the country can possibly hold free and fair elections on Feb. 14 under such disastrous conditions.