Mosque workers and Muslim clerics told reporters of the deaths as they prepared for a mass burial.
The death toll has not been verified independently, and it is not known how many Christians have died.
Nigeria's vice-president has ordered troops to help police restore order and also dispatched top security officials.
It is believed to be the first time Goodluck Jonathan has used executive powers since President Umaru Yar'Adua left Nigeria for hospital treatment in Saudi Arabia in November.
The clashes broke out on Sunday and have continued since, with reports of gunfire and burning buildings...