Most of the deaths occurred in rioting in Maiduguri, capital of north-eastern Borno state. One person died in similar riots in north-central Katsina state.
Witnesses said most of the dead were from Maiduguri's minority Christians.
The cartoonist whose cartoons sparked off the worldwide riots told a Scottish newspaper he had "no regrets".
The riots in Nigeria are the first violent protests in the country over the cartoons.
Eleven churches were torched during the protests and Christian businesses targeted.
The country is nearly equally split between Muslims in the north and Christians.
The BBC's Alex Last in northern Nigeria says the protest had begun peacefully in Maiduguri, and it was not clear what started the violence.
The city's residents described demonstrators running wild after police tried to disperse the protest with teargas.
Crowds of protesters carried machetes, sticks and iron rods through the city centre, the Associated Press news agency reported.
One group threw a tyre around one man, poured gas on him and set him ablaze, it said.
Christian leader Joseph Hayab told Reuters agency that most of those who died had been Christians.
"The Muslim group came out to protest and the security forces tried to ensure it was peaceful, but there were some hoodlums in the crowd and somehow the security forces shot one or two of them," said Mr Hayab.
"They went on the rampage, burning shops and churches of the Christians. The protesters killed the others. Some were even killed in the churches."
Soldiers have been deployed and a curfew imposed. Around 115 people were arrested in Maiduguri and 105 in Katsina.
Borno state governor Modu Sheriff said the state "was shocked and disgusted" by "the civil disturbance" in Maiduguri.
Nigeria has witnessed sectarian violence in the past, and the concern now is that the violence does not spread to other cities, our correspondent says.
Meanwhile the Danish cartoonist whose cartoons provoked the outcry said he did not regret drawing them or having them published.
Kurt Westergaard told the Scottish newspaper, the Glasgow Herald, the cartoons were inspired by "terrorism - which gets its spiritual ammunition from Islam".
Mr Westergaard has gone into hiding since a Pakistani cleric offered a bounty for his death.
The cartoons, first published by Danish newspaper Jyllands-Posten in September and later reprinted by several other European publications, have angered Muslims across the world and sparked sometimes violent protests.
In Libya, at least 10 people died in clashes with police outside an Italian mission on Friday, during a rally over an Italian minister's decision to put the cartoons on T-shirts.
The minister, Roberto Calderoli has resigned, and Libya's interior minister has been suspended as the country investigates the violence.
Source: BBCLast Mod: 20 Eylül 2018, 18:16