The US-led coalition said its forces in northeast Syria Wednesday confronted gunmen with live fire after one of its patrols came under attack near the city of Qamishli.
The Britain-based Syrian Observatory for Human Rights reported a US strike during the clashes in the regime-held village of Khirbet Amo, but coalition spokesman Myles Caggins denied any raid had taken place.
"Coalition forces, conducting a patrol near Qamishli, Syria, encountered a checkpoint occupied by pro-Syrian regime forces," Caggins said, according to AFP.
"The patrol came under small arms fire from unknown individuals. In self-defense, coalition troops returned fire."
Caggins said the patrol returned safely to base after the situation was "de-escalated".
An AFP correspondent saw a US flag flying above an armored vehicle as it left the village.
According to the Observatory, loyalists residing in the village tried to block the passage of a US military patrol, firing in the air.
This prompted a response from US troops, who killed a regime loyalist in the clash, the Observatory said.
The coalition did not report such a casualty.
Khirbet Amo is among the few areas in the largely Kurdish-held northeast controlled by pro-regime forces.
US troops in the region operate as part of the US-led coalition fighting the remnants of the ISIS group.
They routinely carry out patrols in the area alongside their Kurdish allies.