Nigerian police have found several cars and vans filled with explosives in the northern city of Kano, just three days after Boko Haram carried out deadly attacks there, according to officials.
"The police were on a stop-and-search today and in two of the checkpoints, the Boko Haram members on sighting the checkpoints abandoned their vehicles and ran," a high-level police officer told the Reuters news agency on Monday, asking not to be named.
"The vehicles were later checked and the cars were loaded with explosives. Two brand new Hilux open pick-up vans were also found packed with explosives in the Bompai area of Kano."
Authorities discovered at least 10 unexploded car bombs, including one near a police station in Kano, as well as around 100 other explosive devices through the day on Monday.
Al Jazeera's Yvonne Ndege, reporting from Kano, said the cars, which were discovered at a petrol station near the central police station, were "filled with explosive devices that were clearly designed to go off on Friday" but did not.
In reaction to the discovery of the bombs, and potential for the discovery of more explosives, our correspondent said police have been asking for citizens to report any suspicious activities or unattended vehicles parked near symbols of Nigerian authority like police stations and government buildings.
Magaji Musa Majiya, a police spokesperson, said that officers were able to disarm the car bombs.
Security in Nigeria's second largest city has been strengthened since Friday when bomb attacks and fierce gun battles between the sect and police killed at least 178 people. A curfew for the hours between 7pm and 6am has been put in place by local authorities.
According to police figures released on Monday, 29 policemen, three intelligence officers, two immigration officers and scores of civilians were among the dead.
"Nearly all Nigerian security agencies are involved [in trying to figure out] how Boko Haram were able to co-ordinate the attacks. They are trying to beef up authority around the symbols of Nigerian authority" our correspondent said.
In Maiduguri, a town in the north-east that has been at the centre of Boko Haram activity, a policeman was shot dead on Monday.
"The policeman was on patrol along with his colleague in a vehicle when the Boko Haram opened fire and shot him dead," said Simeon Midena, the commissioner of police.
"As usual the killers just disappeared into the crowd."
The joint military task force has increased its defences and widened its patrols in Maiduguri in recent days.
On Sunday, the military killed four suspected Boko Haram gunmen in Maiduguri and found explosives in their car.
"Four members of Boko Haram sect involved in killings in Maiduguri and environs have been under surveillance of security agencies and have been shot dead in Pomomari area of Maiduguri yesterday [Sunday]," Colonel Victor Ebhaleme, an officer in the joint military task force, said in a statement.
"Various IED [improvised explosive device] materials prepared for detonation were recovered from their car."
Boko Haram, which was formed in Maiduguri in 2002, has killed hundreds of people in the last year, mostly in and around its home state of Borno, though its attacks have been spreading across the north of Africa's most populous nation.
The group, loosely modelled on Afghanistan's Taliban, focuses its attacks mostly on the police, military and government, but has also targeted Christians more recently.
It says it is fighting enemies who have wronged its members through violence, arrests or economic neglect and corruption.
Nigerian President Goodluck Jonathan has been severely criticised for not getting a grip on a group that he says has infiltrated the police, military and all areas of government.