Coordinated bomb attacks targeting security forces and gun battles have killed at least 28 people and spread chaos in Nigeria's second-largest city, with bodies littering the streets on Saturday.
A 24-hour curfew was also imposed on the city of Kano, the largest in Nigeria's mainly Muslim north and which exploded into violence on Friday evening, with eight police and immigration offices or residences targeted.
The main newspaper in Nigeria's north reported that a purported spokesman for Islamist group Boko Haram had claimed responsibility for the violence, saying it was in response to authorities' refusal to release their members from custody.
Scores of such attacks in Nigeria's north have been blamed on Boko Haram.
Some 20 huge blasts could be heard in the city as a suicide bomber attacked a regional police office and a car bomb rocked the outside of state police headquarters after the attacker fled and was shot dead, police sources said.
A number of other police posts were targeted, including a secret police building, as well as immigration offices.
Gunshots rang out in several areas, and a local television journalist was among those shot dead as he covered the violence. At least 11 police officers were believed to be among the dead.
"I am now walking along the street of my neighbourhood," Naziru Muhammad, who lives near state police headquarters, said on Saturday morning.
"Between my house and the police headquarters along this street, I have counted 16 dead bodies that litter the streets, six of them policemen."
He said soldiers were in the area collecting the bodies. A police source said two officers had been killed in an attack on a police post, while a medical source said one military personnel and a girl were killed in the same attack.
At least eight others had earlier been reported killed in separate incidents.
"There are heavy casualties around the police headquarters," the police source said on condition of anonymity.
"A lot of civilians have been shot by the attackers. It's difficult to give a death toll, but the number of the dead runs into dozens."
Details began to emerge of the attacks, which were said to include at least two suicide bombers.
At state police headquarters, a would-be suicide bomber sought to join the convoy of the police commissioner, the police source said, but jumped out of the car and sought to escape when officers opened fire. He was shot dead, the source said.
According to a resident, the car rolled over and a huge explosion followed after the would-be bomber tried to flee.
"It was a suicide attempt," the police source said.
"The attacker tried to beat the checkpoint near the police headquarters, but the police opened fire. He jumped out of the car and tried to escape, but he was pursued and gunned down by the policemen."
The shocking attacks, with Kano having escaped the worst of the violence blamed on Boko Haram in recent months, left residents fleeing neighbourhoods and fearing what would come next.
President Goodluck Jonathan declared a state of emergency on 31 December in parts of four states hard hit by attacks blamed on Boko Haram.
Kano was not included in the state of emergency and has not been hit by any of the recent major attacks, most of them having occurred in the country's northeast.
Nigeria, Africa's most populous nation and largest oil producer, is roughly divided between a mainly Muslim north and predominately Christian south.
The state of emergency has not stopped attacks, and the areas targeted have spread beyond the locations covered by the decree.
The limitations of the Nigerian authorities were recently highlighted when the alleged mastermind of a Christmas Day attack outside a church that killed 44 people escaped police custody in suspicious circumstances.
Attacks specifically targeting Christians have also given rise to fears of a wider religious conflict in the country, with Christian leaders warning they would defend themselves. Some have even evoked the possibility of civil war.
However, attacks blamed on Boko Haram have included a wide range of targets, including Muslims.
The group also claimed responsibility for the August suicide bombing of UN headquarters in the capital Abuja that killed 25 people.