The Islamist insurgency in northern Nigeria has entered a more violent phase as militants return to the fight with sophisticated weapons and tactics learned on the battlefields of nearby Mali, Nigerian officials and analysts say.

Hundreds of people have died this year in bombings, shootings and clashes with security forces in this vast region of the country, where the militant group Boko Haram seeks to overthrow the government and install an ultraconservative brand of Islam.

The militants, who traveled to northern Mali last year to join the fight there, have returned with heavy weapons from Libya, presumably from former Libyan leader Moammar Gaddafi’s arsenal. Malian militants also used weapons smuggled in from Libya to seize northern Mali last year.

Boko Haram and an even more radical splinter faction known as Ansaru are also kidnapping Westerners and killing anyone they deem a threat — tactics used by al-Qaeda in the Islamic Maghreb, or AQIM, the terror network’s West and North Africa affiliate, which helped overrun northern Mali last year.

“Boko Haram’s level of audacity was high in the last three or four months. It was exactly after the attacks in Mali,” said a senior local government official who spoke on the condition of anonymity because he is not allowed to comment on security matters. “They were never as audacious as they suddenly became.”

The stepped-up violence is the latest sign that the conflict in northern Mali is spilling into neighboring countries as Islamist militancy spreads across the region.

Last week, suicide bombers in Niger targeted an army barracks and a French-operated uranium mine, killing 26 people and injuring dozens more. Both AQIM and the Movement for Oneness and Jihad in West Africa, an al-Qaeda spinoff in northern Mali, asserted responsibility, saying the attacks were revenge for a four-month-old French-led military intervention in Mali.

France has begun withdrawing some of its forces from Mali, having ousted AQIM and other radical Islamists from towns in the north. Since then, the militants have launched a guerrilla war, orchestrating a campaign of suicide attacks and roadside bombings.

U.N. and regional government officials say Boko Haram and Ansaru fighters traveled to northern Mali to train in AQIM camps and fight alongside the jihadists. In early March, Boko Haram fighters in pickup trucks mounted with heavy guns targeted an army barracks in Nigeria’s Borno state, the militia’s birthplace.

A few days later, Nigerian soldiers raiding a Boko Haram base found more vehicles that had been transformed into fighting machines, suggesting that Boko Haram “has already learned new methods of fighting from the Islamist militants in Mali,” Jacob Zenn, a West Africa analyst, wrote in the CTC Sentinel, the publication of the Combating Terrorism Center at West Point.

“Even if France and its West African allies have driven AQIM out of northern Mali, Ansaru
and Boko Haram are likely self-
sustainable and able to continue attacks.”

Estimated 3,000 killed

Since the death of its leader in police custody in 2009, Boko Haram has carried out more than 700 assaults on police stations, government buildings, mosques and schools in its stronghold of Maiduguri and across the north, killing an estimated 3,000 people. The militia’s name means “Western education is forbidden” in the local Hausa language, and it has publicly praised Osama bin Laden.

In January 2012, hard-line members who opposed the militia’s killing of Muslims defected and launched Ansaru. The group began kidnapping foreigners and forged close ties to AQIM, according to analysts. In January 2013, Ansaru militants ambushed three buses of Nigerian soldiers en route to help the French intervention in northern Mali, killing two soldiers and injuring several others.

By late last year, though, Boko Haram had spread its own ambitions, and some cells appeared to be shifting toward AQIM and Ansaru’s strategy. In February, the militia launched its first cross-border operation, kidnapping a French family of seven in Cameroon and holding them in Nigeria, its first abduction of foreigners. The group said the kidnapping was in response to the French military action in Mali. The family was freed in April after a $3 million ransom was paid, according to the Reuters news agency, although the French and Cameroon governments have denied the reports.

In mid-May, the militia asserted responsibility for its first large-scale incursions. In a May 7 attack on Bama, about 44 miles from Maiduguri, Boko Haram fighters stormed an army base, a police station and government buildings, killing at least 55. The fighters attacked with vehicles mounted with machine guns, similar to the attacks by northern Malian militants.

In a video, Boko Haram leader Abubakar Shekau said his fighters had kidnapped women and children and would treat them as “slaves” in retaliation for the arrests of its members’ wives and children by Nigerian security forces.

The attack on Bama came a few weeks after Boko Haram fighters targeted a military patrol in Baga, a nearby town. Nigerian security forces retaliated by raiding the town, accusing residents of aiding the militants. About 200 people were killed and parts of the town were razed, prompting human rights groups to accuse the military of using excessive force and carrying out extrajudicial killings. Such allegations, which the military denies, have repeatedly arisen over the past three years.

Human rights concerns

Nigeria’s President Goodluck Jonathan stepped up the fight against the Islamists by declaring a state of emergency on May 14 in three northern states, including Borno, of which Maiduguri is the capital. Nigeria has also asked Niger to help in the offensive, underscoring its concern that Boko Haram is trafficking in arms and being helped by foreigners.

Cellphone and Internet networks have been cut to prevent the militants from communicating. In some areas of Maiduguri, the heart of the insurgency, a dusk-to-dawn curfew has been imposed. Long lines of vehicles wait at military checkpoints manned by soldiers across the city.

Human rights activists have warned of abuses amid reports of deaths in rural areas and mass arrests in Maiduguri. An estimated 2,400 people have fled to Niger, according to a statement released last week by the International Committee of the Red Cross.

“Definitely, there will be human rights violations,” said Babangida Labaran Usman, a senior investigation officer with Nigeria’s National Human Rights Commission. “Definitely, innocent people will be killed.”

Nigerian military officials say those being targeted are Boko Haram militants, but Western governments and international human rights organizations have also expressed concern. Secretary of State John F. Kerry recently called on Nigeria to uphold human rights as it tries to quell Boko Haram.

Usman warned that an increase in violations could lead more people to join Boko Haram and Ansaru. “These attacks provoke people, if they have the opportunity, to join the insurgency.”