Police have sent reinforcements to Egypt's southern province of Aswan after at least 23 people were killed in tribal clashes there.
Long-standing tension between Bani Hilal tribesmen and the Nubian Dabudiya family erupted after a woman was accosted last week.
Tribal vendettas are common in Egypt's poor, rural south, but police called the outbreak of violence the worst in recent memory.
The health ministry said 20 people were killed in renewed fighting, a day after a failed reconciliation meeting between the two sides ended in a gun battle that killed three.
It said more than 50 people were injured.
Police said the violence had subsided by this afternoon after they sent in reinforcements.
Because of the scale of the fighting, interim prime minister Ibrahim Mahlab and his interior minister Mohammed Ibrahim both arrived in Aswan this afternoon.
The army also said it had intervened, and accused the Muslim Brotherhood of deposed Islamist president Mohammed Mursi of involvement in the violence.
Since the army ousted Mr Mursi last July, the military-installed authorities have blamed the brotherhood, now designated a "terrorist" organisation, for violence that has rocked Egypt daily for the past nine months.
Police began to reassert themselves across the country only recently, after a breakdown in law and order following a 2011 uprising that overthrew Hosni Mubarak.