(Adds army comment, PM and interior minister visiting Aswan)
CAIRO, April 5 (Reuters) - 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.
The violence erupted late Friday after students from the feuding families had scrawled insulting graffiti on the walls of a school, security sources said.
One family is from the Nubian ethnic group and the other from the Arab Beni Helal clan, the sources said.
The two sides used gunfire and petrol bombs and several houses were burned to the ground before police were able to stop the fighting on Saturday morning, the Interior Ministry said in a statement.
Security sources told Reuters the police and the governor had requested reinforcements from the army on Saturday to prevent more bloodshed.
Army spokesman Ahmed Ali said on his official Facebook page the army had helped to "contain the crisis" and there were "signs of involvement of the Muslim Brotherhood in the strife between the two tribes".
The Islamist group, which has been declared a terrorist organisation by the state, says it is committed to peaceful activism.
Authorities have cracked down hard on the group since the army overthrew elected President Mohamed Mursi of the Brotherhood last year. Thousands of Islamists have been arrested and hundreds more killed.
The prime minister and interior minister travelled to Aswan on Saturday afternoon to meet the governor and discuss plans to quell tensions, MENA reported.
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. (Reporting by Mahmoud Mourad and Maggie Fick; editing by Andrew Roche; editing by Andrew Roche)