At least seven people have been killed in a series of co-ordinated bomb attacks in the northern Nigerian city of Kano, police say.
They say police stations and the regional police headquarters were among the targets. Gunfire has also been heard in several locations.
The militant Islamist group Boko Haram says it carried out the attacks.
The group has been behind a recent campaign of violence in the mainly Muslim north.
Authorities in Kano state have imposed an immediate 24-hour curfew.
Meanwhile, organisers of a controversial civil activists’ mass rally set for Saturday in the commercial capital Lagos called off the event in light of the attacks.
‘Smoke and panic’
In a statement on Friday, police said that “seven casualties have been confirmed from different locations of the attacks” in Nigeria’s second biggest city.
It said that four police stations around the city, the headquarters of the State Security Service, as well as passport and immigration offices were targeted.
A doctor at Aminu Kano Teaching Hospital earlier told the BBC that at least five dead bodies had been brought in.
The BBC’s Yusuf Ibrahim Yakasai in Kano says there was panic in the city as plumes of smoke rose into the sky.
At the scene
Kano is reeling from the bombings that began at about 17:00 local time (16:00 GMT) and rocked this ancient holy Muslim city for more than an hour and a half.
As plumes of smoke rose over the city, residents fled from the streets in panic – not needing the prompt of the 24-hour curfew imposed by the authorities.
A witness at a police station in the south of the city said six gunmen arriving in a car and on a motorbike shot their way into the building before detonating a bomb.
Officers fled the scene – some taking refuge in ditches – and it took the military about 30 minutes to respond by which time the gunmen had escaped.
This seems to have been the pattern of attacks at other stations, except at the Bompai headquarters of the state police in the east of the city where a shoot-out between gunmen and security forces was continuing into the evening.
The roads are now deserted. Some residents are questioning how the security of so many key police buildings could have been compromised.
Another doctor told the BBC that some of the wounded included foreigners from an area near the SSS headquarters, where many expatriates – particularly Lebanese and Indians – live.
There has also been a shoot-out at the headquarters of the state police in the city’s eastern district of Bompai, reports say.
A witness told the BBC’s Hausa Service he was with a group of Christians and Muslims taking refuge in a mosque near the gun battle.
The man – a visitor to the city – said they were lying on the floor, praying together and had turned off the lights. He said his hearing was still affected by the blasts.
One witness told Nigerian television he rushed outside after hearing four explosions.
“On my way out I saw a dead body, a young man lying dead, and then I proceeded further towards the immigration office.
“That was really where the first bomb blast started. There were three dead bodies right there in front of the immigration office and now we also had… several bomb blasts, gunshots… in front of the police station.”
Another local man, Andrew Samuel, said: “I was on the roadside and I just heard a ‘boom’. As I came back, I saw the building of the police headquarters crashing down and I ran for my life.”
A resident near the city centre told the BBC that he had seen bodies being carried out of a police station near the city centre, but did not know if they were injured or dead.
Boko Haram: Timeline of terror
- 2002: Founded
- 2009: Hundreds killed when Maiduguri police stations stormed
- 2009: Boko Haram leader Mohammed Yusuf captured by army, handed to police, later found dead
- Sep 2010: Freed hundreds of prisoners from Maiduguri jail
- Dec 2010: Bombed Jos, killing 80 people and blamed for New Year’s Eve attack on Abuja barracks
- 2010-2011: Dozens killed in Maiduguri shootings
- May 2011: Bombed several states after president’s inauguration
- Jun 2011: Police HQ bombed in Abuja
- Aug 2011: UN HQ bombed in Abuja
- Nov 2011: Co-ordinated bomb and gun attacks in Yobe and Borno states
- Dec 2011: Multiple bomb attacks on Christmas Day kill dozens
- Jan 2012: Hundreds flee areas of north-east Nigeria after a wave of violence
A reporter for the AP news agency said one of the explosions was powerful enough to shake his car several miles away.
Witnesses said the bomber who attacked one of the police stations pulled up outside the building on a motorbike, dismounted and ran inside holding a bag.
Nigeria’s Channels TV said one of its reporters, Enenche Akogwu, had been killed in the attacks.
It said he had been “shot by unknown gunmen suspected to be members of the Boko Haram sect”, outside the state government house.
Police and military roadblocks were put up across the city within minutes, officials told Reuters.
Claim of responsibility
Boko Haram, whose name means “Western education is forbidden”, has said it carried out the attacks.
A spokesman for the group, Abul Qaqa, told journalists in the north-eastern city of Maiduguri, the group’s base, that it had carried out the attacks because the authorities had refused to release members arrested in Kano.
The group wants to establish Islamic law in Nigeria. It started to stage drive-by shootings in 2010 on government targets in Maiduguri.
The death of the Boko Haram leader Muhammed Yusuf whilst being held by police in 2009 is also often cited as the reason for attacks on state institutions by the group, the BBC’s Mark Lobel in Lagos reports.
Analysts say Friday’s blasts were one of Boko Haram’s largest simultaneous attacks, and certainly its largest assault on Kano.
It stepped up its attacks in 2011, targeting police headquarters and the UN in the capital Abuja.
In recent weeks, southerners, who are mostly Christians or animists, living in the north have been the targets of deadly attacks.