"We have discovered over 100 home-made bombs in different parts of the city," said a senior police official on condition of anonymity.
The official said that many unexploded bombs were recovered around the police headquarters which was one of the targets struck in the Friday attacks.
"We have found eight explosive-laden cars abandoned by road sides across the city, including one near a police station and another in a market in a densely-populated area of the city... We are still facing serious security threats," the police officials said.
Meanwhile, hospital workers said the death toll has reached 250 from an earlier toll of 180. Special prayers were conducted in mosques throughout the city to seek divine intervention in order to prevent recurrence of last Friday`s blasts.
Chief Imam of Kano Sani Zaharadeen, traditional ruler of the city Emir Ado Bayero and Governor Rabiu Musa Kwankwaso were present at the prayer session.
About 200 Muslim religious and political leaders offered peace prayers in Kano, an ancient holy Muslim city.
Nigeria`s President Goodluck Jonathan on Monday visited the populous city of Kano after attacks which were unleashed on police stations and other security outfits? office.
He offered his condolences to the people of the city and also went to the Armed Forces Specialist Hospital where some of the wounded were brought for treatment.
Radical Islamist group Boko Haram has claimed responsibility for the attacks.