President Obasanjo meets religious leaders in Kano
The president saw for himself the destruction caused, and also went to an army barracks where several thousand residents displaced by the fighting have taken refuge.
Mr Obasanjo called the violence senseless, and said the Nigerian Government would not tolerate people taking the law into their own hands.
A BBC correspondent in the city says people are still in shock, but that there has been a return to normality, with banks and businesses opening again.
The riots began late on Friday after a peaceful anti-American demonstration by local Muslims.
Returning home
The Nigerian army is maintaining a heavy presence on the streets and while no major outbreaks of violence were reported on Monday, the situation remains tense.
Police say 18 people died in the violence, but the Nigerian Red Cross said in a statement they did not know how many had died but said "it was safe and reliable to quote a figure of over 100".
It also says that at least 18,000 people, most of them non-Muslims, have been displaced by the clashes.
The Red Cross says it has 25 volunteers, providing first aid for those hurt, but it does not give an estimate for the number of casualties in hospitals across the city.
It appears that many people are starting to return to their home areas.
The security forces have been given orders to shoot any rioters on sight.
Leaders meet
Searching for a peaceful solution to the crisis, the governor of Kano state, Rabiu Musa Kwankwaso, called together community leaders on Monday.
It was the first such meeting since the conflict began and was a clear sign the authorities have become aware that deploying the army on to the streets may well be containing the situation but is not enough to defuse the underlying tensions.
What started as a peaceful anti-American demonstration by Muslims on Friday quickly degenerated into running battles, barricades of burning tyres being erected, cars being set alight and buildings torched.
Militant youths from both communities took advantage of the turmoil to loot shops and offices.
Underlying tensions
Our correspondent, who visited Kano at the weekend, says that at its root the dispute is not about American involvement in Afghanistan, but rather the explosion of simmering tensions between the two communities, in a city where tens of thousands of young men have no jobs and no education.
Kano is a majority Muslim city, and Christians there are considered to be outsiders.
Economic hardship and lack of opportunity for education breeds frustration which, as elsewhere across Nigeria, has led to violent unrest.
It is a pattern that has been repeated across this multi-ethnic and multi-religious country in recent years and on occasions leads to death and destruction.
Relations between Christians and Muslims in northern Nigeria have been tense since the extension of Sharia Islamic law in the past 18 months.
In February 2000, more than 2,000 people were killed in religious unrest in Kaduna.
In Jos, last month at least 500 were said to have died in clashes between Muslim and Christians.
The authorities are often reluctant to give out death toll figures for fear of inflaming tensions still further.