Eight soldiers, four allied fighters and three civilian lost their lives.
Gunmen killed at least 15 people in Syria, mostly government soldiers travelling on a bus, in the second such road ambush in recent days, the Britain-based Syrian Observatory for Human Rights said on Monday.
The attack late on Sunday resulted in the deaths of eight soldiers, four allied fighters and three civilians, the war monitor said.
There was no immediate claim of responsibility, but the monitor said the Islamic State jihadist group was to blame. Another 15 people were wounded in an attack in the Wadi al-Azib area.