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The strike Saturday east of the Euphrates River near Dayr Az Zawr hit "a location known to the Russians to contain Syrian Democratic Forces and coalition advisers," the U.S.-led coalition said in a press release.
Several fighters in the Syrian Democratic Forces (SDF) were wounded and required medical care.
The spokesman for the coalition tweeted a photo of medics treating a wounded SDF soldier.
Multinational troops advising and assisting the SDF were present during the strike, but none were injured.
The Russian airstrike came as the Syrian government forces backed by Moscow and the U.S.-led coalition forces are in closer proximity in the battle against ISIS. Syrian regime forces are fighting for Dayr Az Zawr southeast of Raqqa, while SDF continues its offensive north of that city.
In the press release, coalition commander Lt. Gen. Paul E. Funk II seemed to remind Russian forces of the so-called deconfliction line, a communication mechanism used by the Russians and the coalition in Syria to ensure there are no misunderstandings about each other's operations.
"Coalition officials are available and the deconfliction line with Russia is open 24 hours per day," Funk said. "We put our full efforts into preventing unnecessary escalation among forces that share ISIS as our common enemy."
In a Pentagon briefing on Thursday, coalition spokesperson Col. Ryan Dillon said a deconfliction area, where Russia and the coalition seek specifically to avoid any misunderstandings, "starts south of Tabqa and runs west to east and parallels the Euphrates River." He emphasized that the deconfliction communication mechanism was holding, and told reporters the SDF would not enter into the Dayr Az Zawr city center.
In late August, Secretary of Defense James Mattis was asked about the deconfliction line for Dayr Az Zawr.
He said the line was "working ... but every day it's more and more work as we become closer and closer together."
It's unclear if the Russians used the deconfliction communication mechanism prior to Saturday's airstrike.