Around 200 Coptic Christians and Muslims clashed in a southern Egyptian province after a drawing depicting the Prophet Muhammad was posted on a local Christian student's Facebook page.
Troops sealed off several flashpoint villages after angry residents in the province of Assiut, 200 miles south of Cairo, burnt seven Coptic homes in reaction to the drawing.
Muslims generally oppose any depiction of the prophet, even favourable, for fear it could lead to idolatry.
This particular drawing depicted four women asking the prophet's hand in marriage.
The strife began late on Thursday when four homes belonging to relatives of the Coptic student were burned.
Villagers burned another three homes belonging to Copts in nearby villages yesterday. Copts comprise around 10% of Egypt's population.