It was the first major protest to erupt over the issue in Africa's most populous nation. An Associated Press reporter saw mobs of Muslim protesters swarm through the city center with machetes, sticks and iron rods. One group threw a tire around a man, poured gas on him and set him ablaze.
In Libya, the parliament suspended the interior minister after at least 11 people died when his security forces attacked rioters who torched the Italian consulate in Benghazi.
Right-wing Italian Reforms Minister Roberto Calderoli resigned under pressure, accused of fueling the fury in Benghazi by wearing a T-shirt emblazoned with one of the offending cartoons, first published nearly five months ago in a Danish newspaper.
Danish church officials met with a top Muslim cleric in Cairo, meanwhile, but made no significant headway in defusing the conflict.
And in what has become a daily event, tens of thousands of Muslims protested—this time in Britain, Pakistan and Austria—to denounce the perceived insult.
But it was in Nigeria, where mutual suspicions between Christians and Muslims have led to thousands of deaths in recent years, that tensions boiled over into sectarian violence.
Thousands of rioters burned 15 churches in Maiduguri in a three-hour rampage before troops and police reinforcements restored order, Nigerian police spokesman Haz Iwendi said. Security forces arrested dozens of people, Iwendi said.
Chima Ezeoke, a Christian Maiduguri resident, said protesters attacked and looted shops owned by minority Christians, most of them with origins in the country's south.
"Most of the dead were Christians beaten to death on the streets by the rioters," Ezeoke said. Witnesses said three children and a priest were among those killed.
Nigeria, with a population of more than 130 million, is roughly divided between a predominantly Muslim north and a mainly Christian south.
Thousands of people have died in this West African country since 2000 in religious violence fueled by the adoption of the strict Islamic legal code by a dozen states in the north, seen by most Christians as a move to impose religious hegemony on non-Muslims.
The Danish cartoons, including one showing Muhammad wearing a bomb-shaped turban with an ignited fuse, have set off sometimes violent protests around the world.
After the Danish newspaper Jyllands-Posten printed the caricatures in September, other Western newspapers, mostly in Europe, followed suit, asserting their news value and the right to freedom of expression.