Different stories:

A punishing series of U.S.-led coalition airstrikes in Syria last week reportedly killed an unknown number of Russian mercenaries fighting on behalf of the Damascus regime, with some sources saying there were "dozens" of casualties.

(that one)

vs

Fifteen Russians employed in Syria by a private security company have been killed after an explosion rocked an arms depot at their base in the country, according to a monitoring group.

The incident happened at the company’s weapons storage facility at Tabiya Jazira in the northeastern province of Deir Ezzor, said the British-based Syrian Observatory for Human Rights.

(this one)