Nigerian President Goodluck Jonathan, in an address to the nation, has warned that the current postelection unrest recalls events that led to the 1967 civil war.
Nigeria, Africa's most populous nation, is roughly divided in half between the Christian south and the mostly Muslim north.
Riots broke out this week after Jonathan, a Christian from the south, was declared winner of the April 16 election, defeating his rival, a Muslim from the north.
The Red Cross says the violence forced some 40,000 to flee their homes.
The civil war in the 1960s left 1 million Nigerians dead.
Nigeria is due to hold elections for governors and provincial state assemblies next week.
compiled from agency reports