At least 23 people were killed in clashes between rival families in the southern Egyptian city of Aswan, health and security officials said on Saturday.
A man from one group sexually accosted a woman from another, officials said Saturday.
The violence erupted late Friday after students from the feuding families had scrawled insulting graffiti on the walls of a local school, security sources said
The two families hail from a Nubian group and the Arab Beni Helal clan, the sources said.
The two sides used gunfire and petrol bombs and several houses burned to the ground before police were able to stop the fighting on Saturday morning, the Interior Ministry said in a statement.
Mohamed Sorour, a health ministry official in Aswan, told Reuters the number of dead had risen to 23 by Saturday afternoon. He said 31 people were hospitalised.
The governor ordered 17 local schools to cancel classes on Sunday, the first day of the work week in Egypt, state news agency MENA reported.