A top Russian Foreign Ministry official has asserted the United States is to blame for the death of a Russian general killed in eastern Syria over the weekend.

Deputy Foreign Minister Sergei Ryabkov's comments on September 25 were some of the bluntest to date as Russia-backed forces move dangerously close to U.S.-trained and -supplied forces in eastern Syria.

The Russian Defense Ministry said a day earlier that Lieutenant General Valery Asapov had been killed amid shelling near the city of Deir al-Zor.

"The death of the Russian commander is the price, the bloody price for the two-faced American policy in Syria," Ryabkov, was quoted by state-run RIA Novosti and other news agencies as saying.

"The American side declares that it is interested in the elimination of [Islamic State]...but some of its actions show it is doing the opposite and that some political and geopolitical goals are more important for Washington," he said.

Moscow and Washington back separate military forces in the Syrian war, both of which are advancing against Islamic State (IS) militants in the east of the country near the Iraqi border.

There was no immediate response in Washington to Ryabkov's comments. The United States has made similar accusations against Moscow, asserting that Russian forces say they are targeting IS fighters, but are in fact targeting U.S.-backed forces.

Syrian government forces, backed by Russian air power and Iranian-allied militias, have gained control of most of Deir al-Zor on the western side of the Euphrates River.

A U.S.-backed Kurdish-led militia, along with fighters from the Syrian Democratic Forces, said on September 20 that their campaign to capture the IS stronghold of Raqqa, north of Deir al-Zor, was in its final stages.

With the two opposing forces fighting in close proximity to one another, fears have grown that U.S. and Russian air power could be drawn into the fight, and even end up facing one another.

Russia had warned the United States that it would retaliate immediately if Syrian government forces came under fire from the U.S.-backed Kurdish-led militia.

That led U.S. and Russian generals to hold a first face-to-face meeting last week in an effort to avoid accidental clashes and prevent a direct confrontation between the two sides.

Meanwhile, a Syrian Democratic Forces (SDF) spokesman said Russian planes targeted their fighters in gas fields not far from Deir al-Zor.

Brigadier Talal Silo did not specify the number of dead or wounded from the attacks.

The Russian military denied the accusations, saying it conducts accurate air strikes on targets "confirmed by multiple sources."

SDF fighters captured the war-torn country's largest gas field, Koniko, from IS militants on September 23.

Elsewhere in Syria, an activist monitoring group said that Russian air strikes had killed 36 civilians in the northwestern province of Idlib.

Russia, Turkey, and Iran earlier this month agreed to create a "de-escalation zone" in Idlib, an area under the control of opposition forces in the north.

With reporting by RIA Novosti, TASS, and dpa