The Syrian Observatory for Human Rights, a group based in Britain that monitors the war through contacts on the ground, put the Russian death toll at nine. The organization said two clashes in the area over the past five days had left 76 dead on the Syrian government side, including non-Syrians.
The Islamic State used to occupy wide swaths of eastern Syria, including much of the city of Deir al-Zour, the province’s capital, and the city of Raqqa, which the jihadist group considered its capital. The militant group has since been driven from the main urban centers, however.
Still, the region remains a patchwork of armed forces controlling different pieces of territory, leading to frequent clashes and to fears of a larger conflagration over energy resources.
One of the largest such clashes, in February, involved Syrian Army soldiers and Russian mercenaries who tried to seize a gas plant controlled mostly by Kurdish forces and their American military advisers. The ensuing battle left scores of Russians dead.
At first, Russian officials said only four Russian citizens — but perhaps dozens more — had been killed; a Syrian officer said around 100 Syrian soldiers had died.