A break failure caused the tanker to crash into 15 vehicles and two large buses carrying several Iraqi passengers, said Interior Minister Mohammad Khaled al-Rahmoun, while inspecting the site of the accident outside Damascus.
Another 77 people were injured in the accident, he added.
Footage aired on state media showed rescue teams deployed around the mangled remains of two cars.
SANA released photos of the passenger bus with one end blown off.
Victims of the crash are believed to include Iraqi Shia pilgrims visiting holy shrines near the capital.
Holy sites in Syria have remained popular among Shia pilgrims from across the region despite an eight-year war that has displaced millions.