LUXOR, Egypt -- A bloody feud in southern Egypt between an Arab clan and a Nubian family killed at least 23 people in two days of fighting, leaving bodies strewn on hospital floors and homes torched in its wake, government officials and witnesses said Saturday.

An Interior Ministry statement said the fighting in Aswan province erupted over the harassment of a girl and students from the two sides later spray offensive graffiti at local school. Vendetta killings are common in southern Egypt, where perceived violations of honour often spark violence, but this violence apparently raged while security forces did nothing to stop it.

Nubian students' graffiti accused members of the Arab Haleyla clan of working for the former governments of ousted President Hosni Mubarak and overthrown Islamist President Mohammed Morsi, witnesses said. They said offensive graffiti sprayed earlier this week on the school wall accused the Nubians of backing the military after a community delegation met former military chief Abdel-Fattah el-Sissi. El-Sissi, who led the military overthrow of Morsi, is now running for president.

A security official also said tensions come from accusations that some Arab Heleyla members take part in an arm and drugs smuggling ring. Aswan is a way station for a smuggling ring from Sudan. The official spoke on condition of anonymity as he wasn't authorized to speak to journalists.

A Nubian resident who asked not to use his name for fear of retribution said he locked himself and his family inside their house, fearing revenge attacks. He said two members of his family were killed in the fighting.

"There is terror now in the area," he said. "At the outset, we'd call the police and they tell us, 'You work it out."'

Authorities said more than a dozen schools in the area of the infighting will be closed indefinitely until calm is restored.

Footage from the area on social media that appeared consistent with Associated Press reporting showed school children pelting a rival group, despite the presence of an armoured police vehicle before the bloodshed.

Adel Abu Bakr, a Nubian resident of Aswan, said members of the Arab Haleyla first beat a Nubian and then shot dead three Nubians on Friday, including a woman. Another Nubian was killed later that night, he said. Following their funerals, hundreds of Nubians attacked the Arab neighbourhood, killing over a dozen people using mostly sticks and daggers, he said.

Health official Mohammed Azmi told private television station CBC that 23 people were killed and 12 are in critical condition. A local government statement said 31 were injured. Abu Bakr said a local Nubian community centre was set on fire, and other witnesses said seven homes were torched. Ambulances failed to reach the neighbourhood were the two clans live, leaving bodies strewn everywhere.

The Interior Ministry said police officers attempted to negotiate a truce late Friday and arrested three people, but fighting resumed Saturday.

Later Saturday, Prime Minister Ibrahim Mahlab and the interior minister travelled to Aswan to mediate.

Abu Bakr said the police failed to stem the violence and called for the army to intervene.

"The (police) presence would have changed the nature of this fight," he said.

A joint statement from the two clans accused "invisible hands" of igniting the feud. In a Facebook post, military spokesman Col. Ahmed Mohammed Ali blamed members of Morsi's outlawed Muslim Brotherhood group of trying to ignite the fighting. He did not offer evidence to support the claim. Egypt's military-backed interim government routinely blames the group for violence.

Associated Press writer Sarah El Deeb in Cairo contributed to this report.