File Photo: Syrian government forces stand in Kobajjep some 40 kilometres west of Deir Ezzor after taking control of the town as they advance towards Deir Ezzor in the battle against Islamic State (IS) group jihadists on September 5, 2017. AFP
"Nine army soldiers and allied militia fighters were killed in an ambush by the Islamic State" group near oil wells, the Syrian Observatory for Human Rights reported.
The attack was carried out late Sunday in a remote region on the edge of the eastern province of Deir Ezzor where jihadist units have their hideouts, the monitor said.
The rocket attack on a convoy also left 15 pro-government fighters wounded, the UK-based organisation said.
The Syrian state news agency SANA reported five dead in an IS ambush on a military convoy.
The jihadist organisation, which once reigned over a sprawling proto-state straddling swathes of Iraq and Syria, lost its last fixed positions in March 2019 but its remnants have kept up deadly guerrilla-style attacks.
Since the defeat of its self-proclaimed "caliphate", IS attacks have killed close to 1,800 government and allied forces in Syria.
An IS attack on a bus on December 2 killed 10 oil field workers in Deir Ezzor province, the latest in a string of attacks targeting the oil sector.