The Russian Foreign Ministry confirmed Thursday that five Russian nonmilitary citizens were killed in a U.S. strike in Syria on Feb. 7.
Ministry spokeswoman Maria Zakharova said the incident marked the first time Russian combatants in Syria were killed as the result of a U.S. strike.
The incident took place after pro-government forces attacked U.S.-backed Syrian Kurdish fighters in the eastern Deir el-Zour province. The American and Kurdish group hit back with jets, bombers, and drones after the initial attack.
Defense Secretary Jim Mattis called the attack on the Kurdish fighters “perplexing.”
“Why do I say it’s perplexing? I have no idea why they would attack there. The forces were known to be there. Obviously, the Russians knew,” Mattis said.
The deaths threaten to further strain relations between the U.S. and Russia, which is already complicated due to Russia’s interference in the 2016 U.S. elections and questions about President Trump’s relationship with Russian President Vladimir Putin.
