* Islamist sect Boko Haram behind similar past incidents
* Attacks continue in face of military crackdown
* Boko Haram is country's biggest security threat (Updates death toll, adds witness quote)
By Lanre Ola and Ibrahim Mshelizza
MAIDUGURI, Nigeria Jan 14 A car bomb killed at least 29 people on Tuesday in Nigeria's northeastern city of Maiduguri, the epicentre of an Islamist revolt, witnesses said.
No one claimed responsibility for the blast. But militant sect Boko Haram, founded in the city, has repeatedly attacked schools, churches and government and military targets in its four-year-old campaign.
The attack will be a setback for President Goodluck Jonathan's military crackdown, which had temporarily succeeded in pushing Boko Haram's assaults into rural areas.
Boko Haram gunmen stormed the air force base and military barracks around Maiduguri's airport on Dec. 2, ending six months of relative calm in the city.
The bomb, planted in a three-wheel rickshaw taxi, exploded outside the state television offices at around 1.30 pm (1230 GMT), witnesses told Reuters.
"The attack happened just behind the fence of my office. I counted 29 bodies, including two kids and a mother. Lots of others seriously injured," said Abba Kankami, a journalist working at the state television office.
Another witness, Baba Shiek, said he counted 30 bodies.
Military Spokesman Muhammad Dole said in a statement soldiers had arrested one person suspected of being behind what he called "heinous and dastardly acts".
Borno State Police Commissioner Lawan Tanko said 17 people were confirmed dead but the final death toll could be higher.
"TOO MUCH BLOOD"
"I saw two boys on the ground and their bodies cut into pieces, two other cars immediately caught fire and I ran away because there was too much blood," city resident Aisha Hassan told Reuters.
Soldiers fired shots into the air to disperse crowds before cordoning off roads around the scene, witnesses said.
Dozens of youths, some armed with machetes, protested on the street after the attack, accusing politicians of failing to curb Boko Haram.
The violence killed thousands last year. Boko Haram fighters continue to target military outposts and raid villages in remote regions near borders with Cameroon and Chad.
The radical Islamist sect says it is fighting to create an Islamic state in a country of nearly 170 million, split roughly equally between Christians and Muslims.
Maiduguri is the capital of Borno State, where Boko Haram first launched its uprising in 2009, beginning with drive-by shootings of policeman and quickly developing the scale and sophistication of its attacks.
Tuesday is a public holiday in Nigeria, as millions of Muslims mark the Prophet Mohammad's birthday.
Boko Haram and splinter Islamist groups are viewed as the biggest security threat in Africa's second largest economy and biggest oil producer.
The United States and its allies are increasingly concerned that Islamist groups in Nigeria will strengthen ties with al Qaeda's north African wing.
A Boko Haram suicide attack on the United Nations building in 2011 in the capital Abuja killed at least 25 people. (Additional reporting by Isaac Abrak in Kaduna; Writing by Joe Brock; Editing by Andrew Roche)