Investigators on Monday combed the scene of a suicide car bomb attack that killed four in the north Nigerian city of Kano, as police said they had foiled a second blast.
Authorities said it was too early to say who was behind the violence but observers suggested a link to local politics rather than Boko Haram, the Islamist insurgents terrorising north Nigeria who are holding more than 200 schoolgirls captive.
The scene of Sunday`s blast in the mainly Christian district of Sabon Gari was cordoned off, with armed police and soldiers on guard and allowing only local residents back home.
Police meanwhile said officers had averted another car bomb attack in the city after stopping a car packed with material for a home-made bomb.
"Kano police operatives, acting on intelligence, tracked and recovered a Mitsubishi station wagon car... loaded with assorted gas cylinders, one container of fuel and other electrical components of improvised explosive devices," a statement read.
"The vehicle was recovered at Tafawa Balewa Street, (in the) Nasarawa area of Kano state, and has since been rendered safe by police bomb disposal experts.
"Meanwhile, security agencies in Kano have commenced (an) investigation into both the aborted blast as well as last night`s bomb incident."
Sunday`s attack happened at about 10:00 pm (2100 GMT) in the Middle Road area of the neighbourhood on Sunday, when the busy area was packed with revellers at its many bars and restaurants.
Windows on the two-storey buildings lining the road were smashed and the burnt-out remains of five cars, plus the attackers` vehicle, were left on the roadside.
Kano police commissioner Adelere Shinaba told reporters that it was soon early to say who was responsible for the attack, which is the second time in less than a year that Sabon Giri has been targeted.
Three men and a young girl aged 12 were killed in the blast, he added. Seven others were injured. Last July, a series of explosions rocked the Sabon Gari area, killing 12 with outdoor bars the apparent target. The military at the time blamed Boko Haram Islamists for carrying out the bombings.
The extremists have in the past inflicted heavy violence on Kano, which is Nigeria`s second-biggest city and a commercial hub for the whole of the Muslim-majority north.
But some observers were quick to make a link between the blast and local government elections held in Kano on Saturday, at which the main opposition All Progressives Congress (APC) won all 44 seats.
The last local elections were held seven years ago and the announcement of the results triggered widespread violence. Security had been tight in the city in the run-up to the latest poll.
Northern Nigeria has been hit by five years of increasingly bloody attacks at the hands of Boko Haram and a mounting civilian death toll.
On Saturday, President Goodluck Jonathan and his counterparts from Benin, Niger, Chad and Cameroon vowed to step up cooperation to target the group seen as a threat to regional stability.
On the eve of the summit, suspected militant fighters kidnapped 10 Chinese construction workers from northern Cameroon.
The authorities in Yaounde said it was likely that they had been taken back across the border into Nigeria.
The United States, which has branded Boko Haram an international terrorist group, said UN sanctions could be imposed on it.
An international search is on involving the United States, Britain, France and Israel to help find 223 schoolgirls still missing after they were kidnapped in Chibok, northeast Borno state, on April 14.
Jonathan, under pressure because of his handling of the affair, has ruled out negotiations for their release, after Boko Haram leader Abubakar Shekau indicated they may be freed in a prisoner exchange.