Gunmen killed at least 15 people in Syria, mostly government soldiers travelling on a bus in the second such road ambush in recent days, a war monitor said Monday.

The ambush late Sunday resulted in the deaths of eight soldiers, four allied fighters and three civilians, the Britain-based Syrian Observatory for Human Rights said, updating an earlier toll.

There was no immediate claim of responsibility, but the monitor said the Islamic State group was to blame. Another 15 people were wounded, with cars and fuel tankers also attacked, in the Wadi al-Azib area of Hama province.

Syria's official news agency SANA said the "terrorist attack" killed nine people, all civilians. Last week, the IS group said it ambushed a bus on December 30 in Syria's eastern Deir Ezzor province, killing at least 37 soldiers.

The extremist group overran large parts of Syria and Iraq and proclaimed a cross-border "caliphate" there in 2014, before multiple offensives in the two countries led to its territorial defeat.

The group was overcome in Syria in March 2019, but sleeper cells continue to launch attacks. More than 387,000 people have been killed and millions forced from their homes since Syria's civil war broke out in 2011.