A source close to the Syrian government confirmed the strike and said there had been casualties and vehicles destroyed. It would be the first time coalition warplanes had hit Syrian government forces.
The Observatory said the strike hit part of the Saeqa military camp near the town of Ayyash in western Deir al Zor province and wounded 14 military personnel in the first such incident since the coalition began its bombing campaign against IS in Syria.
The US-led force's campaign is against Islamic State, which controls most of Deir al Zor, including its capital, and has regularly targeted the group in the eastern Syrian province.