Why has fighting started again in Syria's Deir al-Zour?

At least two people were killed in clashes in Deir al-Zour province in eastern Syria on Wednesday, as tribal fighters believed to be backed by the Assad regime and Iran clashed with the US-backed Kurdish-led Syrian Democratic Forces (SDF).

This is the worst flare-up in violence between the tribal fighters and the SDF in eleven months.

Fighters from the Kurdish-led SDF have controlled most of northeastern Syria ever since the territorial defeat of the Islamic State militant group in 2019.

While the Kurdish-led People’s Protection Units (YPG) are the main component of the SDF coalition of militias, Syrian Arab groups play an important role in keeping the Arab-majority areas of northeastern Syria under control.

However, in September 2023, the Deir al-Zour Military Council made up of tribal fighters from the province, revolted against their erstwhile SDF allies after the SDF decided to arrest their commander Ahmed Al-Khubail, also known as Abu Khawla.

The SDF accused Abu Khawla of abusing his power, being involved in the drug trade and colluding with the Syrian regime while turning a blind eye to the Islamic State (IS) group, whose fighters are still active in eastern Syria despite their 2019 territorial defeat.

Clashes between the tribal fighters, who are now commanded by Ibrahim al-Hafil and the SDF on the east side of the Euphrates, have continued sporadically ever since.

After the latest flare-up, which took place in the villages of Dhiban, Latwa, and Abu Hamam, the SDF described the tribal fighters as "Syrian regime-backed mercenaries".

The Syrian opposition news site Enab Baladi said it had seen a video showing Hashem Al-Sattam, the head of an Iranian-backed militia in Deir al-Zour called the "Sons of the Jazira and Euphrates Movement" taking part in fighting in Dhiban but added that it was unverified.

The Syrian regime controls areas of Deir al-Zour province west of the Euphrates River, and militias associated with its ally Iran have a heavy presence there.

The village of Dhiban is near the strategic al-Omar oil field, where the US military has a presence.

The SDF imposed a curfew in areas on the east bank of the Euphrates, warning anyone who violates it that they faced arrest and trial.

The UK-based Syrian Observatory for Human Rights (SOHR) said the SDF brought reinforcements to the area as the fighting continued Wednesday.

Enab Baladi reported that civilians had fled the area as the clashes continued.

The unstable situation in the wider Middle East region, with Iran-backed militias previously targeting US forces in what they say is a response to US ally Israel’s brutal war on Gaza has further complicated the situation.

It remains to be seen if what is happening in Deir al-Zour is a temporary flare-up in an unstable area or will escalate into a more serious conflict.