Choji Gyang, a religious adviser to the government of Plateau state, told CNN the Christians attacked a mosque Monday where Muslims had gathered. The mosque had been burned in previous religious violence.
Jos is on the border between Muslim-majority northern Nigeria and the Christian-majority south. Religious violence has been endemic for months in the city and villages surrounding it, starting Christmas Eve with the bombing of Christian targets.
At least 20 people were killed Monday and Tuesday, Gyang said, most of them after the military fired into crowds of protesters.
A Nigerian newspaper, The Daily Champion, said the trouble started Monday when young men set up road blocks to stop Muslims from getting to prayers. Officials said some Muslims responded by pulling out knives.