Syrian regime forces conducted artillery strikes “in the vicinity of” Syrian Democratic Forces positions near Deir Ezzor on Monday, a spokesperson for the US-led Coalition said.

The SDF blamed both Russia and Syrian regime forces for what its general command said were strikes by aircraft and artillery on three locations near Deir Ezzor that killed one and injured two of its personnel. The Russian defense ministry later denied responsibility for the strikes.

“Russian-backed Syrian regime forces conducted artillery strikes in the vicinity of Syrian Democratic Forces fighting positions northeast of Dayr az Zawr Sept. 25,” the spokesperson said in an email to The Globe Post on Tuesday.

“SDF immediately reported the impacts in their area, and later announced casualties. Coalition officials passed SDF and impact locations to the Russians through the de-confliction line with the intent to inform Syrian regime forces of impacts on or near SDF positions.”

The spokesperson said that Coalition advisors were not present at the time of the attack, but warned that the regime’s imprecise targeting “endangers both the SDF and Coalition members.”

Coalition officials continue to use the de-confliction line to prevent “accidental targeting or escalations in tension or the use of force” between the regime and its allies and the SDF and its partners, the spokesperson said.

The spokesperson did not confirm reports that the SDF later returned fire on positions it suspected it was targeted from. However, the spokesperson said the Coalition “remains in contact with [the SDF] to ensure support of the mission to defeat our shared partner.”

Asked if the recent strikes on SDF positions could cause issues with Coalition and SDF plans for operations the Khabur river valley and further along the Euphrates river valley, the spokesperson simply said: “SDF operations to liberate lands in eastern Syria from ISIS continue unabated and the de-confliction line with Russia remains open.”

On Tuesday, SDF forces advanced toward As Suwar on the Khabur river, around 35 kilometers (22 miles) northeast of the oil fields, capturing the town according to some reports.

Tense times in Deir Ezzor

Monday’s incident came less than a day after Russia’s most senior military officer in Syria, Lt. Gen. Valeriy Asapov, died after ISIS mortars struck a Syrian regime headquarters near Deir Ezzor.

Russia on September 21 warned the United States that any attempts to fire on Russian or Syrian troops near Deir Ezzor from areas controlled by the SDF would result in immediate retaliation, just days after the US-led Coalition blamed Russia for a September 16 strike on SDF fighters near Deir Ezzor. A Coalition statement said that the location was known to Russia to “contain Syrian Democratic Forces and Coalition advisors.”

Oil-rich Deir Ezzor is the only Syrian province where ISIS still holds significant territory. Syrian government and allied forces including Russia are mounting an anti-ISIS offensive west of the Euphrates river while the SDF is conducting a Coalition-backed campaign against ISIS on the east side, where the majority of Syria’s oil wells are located.