Nigeria has reinforced security in northern areas, as clashes between Muslims and Christians erupted for a second day in the city of Kano. Health workers say as many as 25 people have been killed.

Central parts of the northern city of Kano and main Christian areas where troops and police were out in force returned to calm on Wednesday.

But smoke could be seen rising from the city's outlying areas. For a second day, Muslim youths lit fires, set up barricades and attacked Christians who tried to flee aboard buses and police vehicles.

Muslim gangs wielding machetes and throwing rocks and gas canisters, on Tuesday attacked churches, shops, vehicles and homes in the main minority Christian areas.

Just before the violence erupted, Muslim clerics had called on the federal government to stop recent attacks against Muslim communities in nearby Plateau state. Government officials say those attacks by Christian ethnic Tarok militias, claimed between 200 and 300 lives, but the deployment of 600 extra police officers has restored calm.

Meanwhile, leaflets calling on Muslims to avenge the violence in Plateau state are circulating in the northern city of Bauchi, prompting authorities to increase security there, as well.

Nigerian analyst Tunde Martins says he believes the situation will be contained, but that the eruption of big city violence is inevitable.

"The Muslim leaders in Kano have been speaking to their faithful to kind of exercise restraint," he said. "It was expected that there will have been some backlash and reaction, especially from the core Muslim areas."

President Olusegun Obasanjo has been holding crisis talks with Muslim leaders this week, and vowed those responsible for the attacks in Plateau state will be punished.

Christian militia leaders there said they were avenging previous attacks by the mainly Muslim ethnic Hausa-Fulani cattle traders against Tarok farmers.

Mr. Martins says local ethnic hostility, usually involving land ownership and political power, should be solved locally.

"There is a need for more community education in the north-central part of Nigeria to allay these fears of people who have allowed little problems within themselves, like issues of land and farm and other things, [to] degenerate into the issue of religious differences," he said. "I believe there is a need for the community itself, the communities to be deeply involved, as the government has kind of left the whole situation in their hands."

Since the end of military rule in Nigeria and the arrival of democracy in 1999, an estimated 10,000 people have been killed in sectarian and ethnic clashes.