The Associated Press
People gather around a minibus struck in an apparent explosion as it sits near a highway overpass in Kaduna, Nigeria, on Tuesday, Feb. 7, 2012. Two explosions struck Tuesday near army and air force bases on the outskirts of the central Nigerian city at the heart of riots last year that killed hundreds, officials said . (AP Photo)

LAGOS, Nigeria — Bombs exploded Tuesday outside of two major military bases on the outskirts of a central Nigerian city at the heart of ethnic and religious unrest in Africa's most populous nation, injuring an unknown number of people.

The attacks came as a radical Islamist sect known as Boko Haram launches increasingly bloody attacks on Nigeria's weak central government. No one immediately claimed Tuesday's bombings, though suspicions quickly fell on the sect, even as state-run television aired a purported video Tuesday from the group claiming it welcomed peace talks with the government.

The blasts struck near the Nigerian army's 1st Mechanized Division headquarters and the training command of the Nigerian air force near Kaduna, officials said. Soldiers and security agencies quickly shut down access to the two areas, with some seizing the cameras of working journalists.

A third explosion occurred near a highway overpass, though officials had no other details about it.

It was unclear how many people were injured in the attacks, though witnesses said they saw injured soldiers wearing blood-drenched uniforms after the blasts. At the 1st Mechanized Division, the glass windows of the division's headquarters had been blown apart by the power of the explosion.

Maj. Gen. Raphael Isa, an army spokesman, said in a statement that a suicide bomber dressed in a military uniform attempted to drive a car bomb into the division headquarters. Soldiers guarding the gate opened fire on the man, who died from gunshot wounds.

"The suicide bomber was the only casualty," Isa said.

An air force spokesman could not be immediately reached for comment, though military officials in Nigeria often downplay casualties suffered by their personnel.

Kaduna, on Nigeria's dividing line between its largely Christian south and Muslim north, was at the heart of postelection violence in April. Mobs armed with machetes and poison-tipped arrows took over streets of Kaduna and the state's rural countryside after election officials declared President Goodluck Jonathan the winner. Followers of his main opponent, former military ruler Muhammadu Buhari, a Muslim, quickly alleged the vote had been rigged, though observers largely declared the vote fair.

Across the nation, at least 800 people died in that rioting, Human Rights Watch said. In the time since, heavily armed soldiers remain on guard on roadways throughout Kaduna. In December, an explosion at an auto parts market in Kaduna killed at least seven people. Though authorities said it came from a leaking gas cylinder, the Nigerian Red Cross later said in an internal report the blast came from a bomb.

The bombings in Kaduna come amid an increase in sectarian attacks by the sect known as Boko Haram. Its members have been blamed for killing at least 270 people this year alone, according to an Associated Press count. Its violence comes as part of a campaign its leader Abubakar Shekau describes as avenging Muslim deaths and pushing for strict Shariah law across multiethnic Nigeria, a nation of more than 160 million people.

Tuesday's blasts also come after security agencies last week arrested a man they believe to be the sect's spokesman.

Politicians, including President Goodluck Jonathan, a Christian, have suggested Boko Haram should negotiate with the government for peace. However, Shekau has struck an increasingly violent tone in videos purportedly posted by the sect to the Internet, including saying: "I will enjoy killing (those against us) like I am killing a chicken."

On Tuesday, the state-run Nigerian Television Authority aired a purported video from members of the sect. The short video, which the channel said came from "some unidentified sources," showed two people wearing masks over their faces and talking about possible peace negotiations as a "welcome development."

The men also named several people who could negotiate on the behalf of the sect.

"The decision taken by this men can really change the entire situation, their word is our word, we trust and respect them, they are the best messengers between us and the government," one man said.

Diplomats and security officials believe the sect has splintered into several wings over time, with one violent arm remaining in contact with two al-Qaida-inspired terror groups in Africa. Officials hope to negotiate with other, more peaceful members of the sect.

However, an attempt in September by former President Olusegun Obasanjo to reach out to the sect saw the go-between killed less than two days later.

An Associated Press writer in Kaduna, Nigeria, as well as AP writer Bashir Adigun in Abuja, Nigeria, contributed to this report.

Jon Gambrell can be reached at www.twitter.com/jongambrellAP.