An airstrike on a vehicle in eastern Syria near the porous border with Iraq killed at least five fighters from pro-Iran units, two security sources in the region told Reuters.
One of the sources said the strike was carried out by a drone, but could not specify which military the drone belonged to. The second source said it targeted fighters as they changed shifts at a checkpoint.
Swathes of Syria's eastern border with Iraq are controlled by armed groups aligned with Iran and who fought on behalf of Syria's armed forces throughout the country's civil war.
They include Iraqi armed groups that also control the Iraqi side of the frontier.
The border is now a smuggling hub, with weapons brought across from Iraq into Syria and other goods flowing into Iraq.
The US and Israel have both carried out strikes in Syria against Iran-aligned factions in the past.
