(Photo: AP Photo/Abdulkareem Haruna)

MAIDUGURI, Nigeria (AP) — A vehicle exploded at a military post in a commercial area of a northeastern Nigerian city Tuesday, killing at least 17 people and causing pandemonium, with blood-spattered bystanders running away and vehicles colliding as drivers fled.

Police said a suicide bomber is suspected in the lunchtime blast in Maiduguri, the birthplace of Boko Haram, an Islamic extremist network that has been terrorizing northeast Nigeria.

Soldiers started firing automatic rifles in the air after the explosion sent a dense column of dark smoke into the air. The blast occurred at 1:30 p.m. in front of a large military post called JTF Sector 4. A nearby vehicle also burst into flames.

A woman who may have lost a loved one raised her hands above her head and shouted: "I am finished. I am finished!"

Police Commissioner Lawan Tanko said 17 corpses were recovered at the scene but others could have been taken to nearby hospitals.

"It was a suicide bombing that was carried out in a pickup van loaded with firewood," he told The Associated Press. Fifteen vehicles and four motorcycle taxis were destroyed, he said.

Thousands of people have been killed in the insurgency affecting parts of Nigeria's predominantly Muslim northern half.

President Goodluck Jonathan declared a state of emergency in May to quell it and thousands of security forces were deployed to the area. They swiftly drove militants out of Maiduguri and most other cities, but the insurgents have begun striking back in the urban centers.

On Dec. 2, hundreds of Boko Haram fighters in trucks and a stolen armored personnel carrier attacked an air force base on the outskirts of Maiduguri in one of the insurgent group's most daring attacks. Two helicopters and three decommissioned military aircraft were heavily damaged.

A U.S. travel advisory issued earlier in January said, "Late 2013 saw an increase in Boko Haram attacks and clashes with Nigerian government security forces in northern Nigeria. ... Boko Haram is known to descend on whole towns, robbing banks and businesses, attacking police and military installations, and setting fire to private homes."

The Islamic extremist uprising began in 2009 and threatens the security and cohesion of Africa's biggest oil producer and its most populous nation, with more than 160 million people. The extremists say they want to impose Islamic Shariah law across all of Nigeria.

In one of the group's highest-profile attacks, a Boko Haram member detonated a car bomb at the U.N.'s main offices in Nigeria's capital, Abuja, on Aug. 26, 2011, killing 25 people and wounding more than 100. The United States last year designated Boko Haram a terrorist organization.

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