Dozens of people are said to have been killed during days of clashes between a US-backed, Kurdish-led militia and Arab tribal fighters in Syria.
The fighting erupted after the Syrian Democratic Forces (SDF) arrested the head of a tribal militia backed by Arab clans with which it worked in the eastern province of Deir al-Zour.
The unrest later spread north and west to Hassakeh and Aleppo provinces.
The UN has received unconfirmed reports of 54 civilians dying in attacks.
Critical infrastructure is also said to have been destroyed or damaged, including at least two hospitals and three water treatment facilities.
The US, which has hundreds of troops in SDF-controlled areas to counter the jihadist group Islamic State (IS), has urged all sides to cease fighting immediately and come to a peaceful resolution.
A US-led global coalition relied heavily on the SDF and its allies to drive IS militants out of tens of thousands of square kilometres of northern and eastern Syria between 2015 and 2019.
The Syrian government controls adjoining territory west of the River Euphrates, along with allied militias backed by Iran.
The government accuses the SDF of “separatism”, but they have largely avoided conflict during the 12-year civil war.
Rebel factions supported by Turkey, meanwhile, control neighbouring stretches of land along Syria’s northern border.
—BBC
