- At least 11 IS jihadists were also killed, the Observatory added.
BEIRUT: The Islamic State group Monday ambushed a regime convoy in eastern Syria, killing at least 26 fighters, including seven Syrian troops, a war monitor said.
The Britain-based Syrian Observatory for Human Rights said the early morning ambush in the province of Deir Ezzor came as the convoy combed the area for jihadists, after a string of recent attacks.
"Violent clashes between the two sides led to large human losses," it said, calling the toll from fighting the "largest since the start of the year".
Observatory head Rami Abdel Rahman said at least seven of the 26 killed were Syrian troops, while the remaining casualties were mostly Syrian militia fighters.
At least 11 IS jihadists were also killed, the Observatory added.
The jihadist group overran large parts of Syria and Iraq and proclaimed a cross-border "caliphate" in 2014, before multiple offensives in the two countries led to its territorial defeat.
The group lost its last scrap of territory in Syria in March 2019, but in recent months it has ramped up attacks against regime forces, especially in the east of the country bordering Iraq.
Last week, IS jihadists killed 19 Syrian regime fighters and allied militia forces in central Syria.
And in December, nearly 40 Syrian troops were killed when IS ambushed a bus carrying soldiers travelling home for the holidays.
The desert area in Deir Ezzor province provides a "safe haven" for jihadists planning attacks on regime forces and other rivals, the United Nations said in a report published this month.
IS retains some 10,000 active fighters in Iraq and Syria, although the majority are reported to be in Iraq, the UN has said.
The war in Syria has killed more than 387,000 people since it started in 2011, the Observatory says.