DAMASCUS - US forces have carried out a sudden withdrawal from two major military bases in Syria's eastern Deir ez-Zor province, the Syrian Observatory for Human Rights said Monday, in what marks one of the most significant American military shifts in northeastern Syria.

According to the Britain-based monitoring group, the withdrawal began gradually on May 18 and accelerated over the past 48 hours. US military convoys, including armored vehicles and logistical equipment, were seen departing the al-Omar oil field and the Conoco gas field, both strategic outposts within the area controlled by the US-backed Syrian Democratic Forces (SDF).

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The pullout took place amid intense overflights by aircraft from the US-led international coalition, the report added.

Following the withdrawal, the SDF special forces commandos were deployed to the vacated locations.

Sources cited by the observatory said that while American ground troops have withdrawn from these two sites, joint operations targeting Islamic State (IS) militants will continue with coalition support based out of the al-Shaddadi base in southern al-Hasakah province, where US forces still maintain a presence.

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The move has sparked concerns over a potential security vacuum in a region already grappling with instability, recurring IS activity, and mounting local tensions, according to the observatory.

The observatory noted that while the US exit from these positions does not mark a full withdrawal, it is nonetheless one of the most significant repositionings of American troops in the area.