The figures could not be independently confirmed.

Residents said sporadic gunfire could be heard in many neighbourhoods and several houses were on fire, but the violence had not spread beyond the city itself.

Security forces are trying to prevent a repetition of clashes in November 2008, in which hundreds of residents were killed in the country's worst fighting between Muslim and Christian gangs in years.

Curfew imposed

Earlier on Tuesday, Gregory Anyating, the state's police commissioner, said: "In view of this situation in town, I hereby declare a 24-hour curfew starting from now."

Goodluck Jonathan, the Nigerian vice-president, who has taken over ceremonial duties from Umaru Yar'Adua, the ailing president, has directed the national security adviser and senior police officials to take the necessary action to restore calm to the city.

 
Ima Niboro, the vice-president's spokesman, said: "I assure you that the federal government is on top of the situation in Jos and the situation is under control."

This week's violence started after an argument between Muslim and Christian neighbours over the rebuilding of homes destroyed in the 2008 clashes.

Nigeria has roughly equal numbers of Christians and Muslims, although traditional animist beliefs underpin many people's faiths.

More than 200 ethnic groups generally live peacefully side by side in the West African country, although one million people were killed in a civil war between 1967 and 1970 and there have been outbreaks of religious unrest since then.

At least 40 people were killed last month in clashes between Nigerian security forces and members of an Islamic sect in the northern city of Bauchi.