LAGOS, Nigeria (AP) -- At first, the Islamic extremists in Nigeria's dusty northeast rode on the backs of motorcycles, firing on government officials and other perceived enemies with worn Kalashnikov assault rifles hidden beneath their flowing robes. Now, they come prepared for war.
When Islamic fighters drove into a town in northeast Nigeria on Tuesday, they used anti-aircraft guns, mounted on the backs of trucks, to destroy nearly every landmark of the nation's federal government. Fighters also rode in on at least one bus, the military said, while in other assaults insurgents have fired rocket-propelled grenades.
The militarization of Islamic radicals in the north comes after witnesses saw Nigerian fighters mingle with the extremists who took over northern Mali in the weeks following a coup there. It also comes after fighters seized massive troves of Nigerian military equipment and have received access to arms smuggled out of the lawlessness of Libya.
Those new arms, and the willingness of extremists to use them, highlight the increasing instability in Nigeria's north and ever-growing dangers facing the nation's weak central government.
"Each year, they grow in prominence and sophistication," said David Zounmenou, an analyst at the Institute for Security Studies in Pretoria, South Africa. "That's what's making the fighting that much more difficult for the Nigerian security forces."
Tuesday, the sophistication of the fighters, likely from the extremist network known as Boko Haram, could be seen in their assault on Bama, a town some 65 kilometers (40 miles) southeast of Maiduguri, the capital of Borno state. The military said some 200 fighters in buses and pickup trucks lay siege to the town. In their arsenal were truck-mounted anti-aircraft guns, weapons seen during the civil war in Libya and the recent fighting in northern Mali.
That attack in Bama killed at least 42 people, as well as 13 others that authorities described as Boko Haram fighters. But the insurgents' heavy weapons helped them overrun the barracks of the Nigerian Army's 202nd Battalion, as well as a police station, a police barracks, a magistrate's court, local government offices and a federal prison. The extremist fighters freed 105 prisoners during their assault, Lt. Col. Sagir Musa said.
The use of the weapons marks a transformation of Nigeria's Islamic extremist insurgency, which grew out of a 2009 riot led by Boko Haram members in Maiduguri that ended in a military and police crackdown that killed some 700 people. The group's leader died in police custody in an apparent execution, fueling dissent that broke into the open in 2010 with the targeted killings of government officials, security agents and religious leaders who spoke out against Boko Haram.
Since then, Islamic extremists have engaged in hit-and-run shootings and suicide bombings, attacks that have killed at least 1,618 people during that time, according to an Associated Press count. That number doesn't include the killings of at least 187 people in the fishing village of Baga during fighting between extremists and security forces, as witnesses and human rights activists say Nigeria's military killed civilians and burned thousands of homes and businesses.
Extremist attack casualties are expected to rise as fighters now have access to sophisticated weaponry. While Nigeria's military has fought in the past decade with heavily armed militants and criminal gangs operating in the creeks of its oil-rich southern delta, analysts and security official say those groups never had access to anti-aircraft weapons. Nor did these groups launch attacks overrunning military barracks or leveling towns.
Where extremists gathered these sophisticated weapons also remains unclear, though they have several means available to them. A propaganda video released in March by Boko Haram, featuring its leader Abubakar Shekau, showed fighters gathered around weapons they said they stole from an attack on an army barracks. Those weapons included what appeared to be heavy machine guns, rocket-propelled grenades and possibly anti-aircraft weapons, as well as ammunition and brand-new bulletproof vests.
Another source of tactics and weapons may come from northern Mali, where Nigerian extremists fought along others.
"Boko Haram will also likely recruit militants who fought and obtained new skills from warfare in Mali," wrote analyst Jacob Zenn in a recent publication by the Combating Terrorism Center at the U.S. Army's West Point. "The Boko Haram attack on an army barracks in Monguno ... , in which the militants mounted weapons on four-wheel-drive vehicles, and the discovery of improvised fighting vehicles in a raid on a Boko Haram hideout in Maiduguri ... suggest that Boko Haram has already learned new methods of fighting from the Islamist militants in Mali."