A blast hit Kano on Sunday, in a street with many bars and night spots.
Scores were feared dead in the explosion which witnesses quoted by the AFP news agency said was caused by a suspected car bomb.
The blast took place in an area mostly inhabited by Christians from southern Nigeria, the Reuters news agency reports.
The militant Islamist group Boko Haram has carried out attacks in Kano State.
Witnesses quoted by AFP said that the blast could be heard from several miles away and happened on a busy road lined with bars in the predominantly Christian area of Sabon Gari.
The blast comes as the Nigerian authorities continue the search for more than 200 schoolgirls kidnapped by Boko Haram.
Kano police spokesman, Musa Majiya, said it was too early to say if the blast in the Sabon Gari or “foreign quarter” of the North’s biggest city had caused any casualties.
But witness Abdul Dafar, who lives a block away, told Reuters he saw at least four dead bodies after the explosion.
“I heard a loud blast. And there was a lot of smoke. Soldiers came in to cordon off the place and ambulances were rushing people to hospital,” he said.
There was no immediate claim of responsibility, but blame is likely to fall on Boko Haram, whose struggle against the Nigerian state has killed at least 12,000 in the last five years.
The militants also operate in neighbouring Niger, Cameroon and Chad, and President Goodluck Jonathan described them as West Africa’s Al-Qaeda on Saturday in Paris, where regional leaders met France’s President Francois Hollande to discuss how to tackle the growing threat posed by the group.
The Islamists grabbed world headlines with abduction of more than 200 schoolgirls a month ago from a remote village in the North-East. Britain, the United States and France have pledged to help rescue them.
Boko Haram has frequently attacked Sabon Gari, whose liquor stores are also a cause of friction with Kano’s Islamic police.