MOSCOW -- The Russian military denied claims on Sunday that it struck a U.S.-backed force in eastern Syria, wounding six fighters.

The Kurdish-led and U.S.-supported Syrian Democratic Forces said Saturday that its fighters had been hit in the airstrike near the eastern city of Deir el-Zour in an industrial area that recently had been liberated from the Islamic State group.

Western forces embedded with the SDF were not injured, the U.S. military said. The SDF is supported by a U.S.-led international coalition of forces to defeat IS militants in Syria and Iraq. An estimated 900 U.S. troops are embedded with partner forces in Syria. They provide artillery support and can command air support.

Russian Defence Ministry spokesman Maj. Gen. Igor Konashenkov said: "Russian air forces carry out pinpoint strikes only on IS targets that have been observed and confirmed through several channels."

SDF fighters have been advancing against IS fighters on the east bank of the Euphrates while Syrian government forces and their allies are pushing on the western side against the jihadists.

The march by the SDF aims to prevent Syrian troops and their allies from expanding their presence along the border with Iraq.

Also Sunday, the U.N.'s World Food Program halted its air drops to Deir El Zour after its trucks were to reach the city with food relief, for the first time since May 2014.

A five truck convoy brought with it enough wheat to feed 70,000 people, the organization said in a statement. Monitoring groups reported that residents were receiving wheat distributions the same day.

With the city besieged by militants from the Islamic State group, the WFP began delivering aid through high-altitude air drops in April last year. It flew missions five times a week and completed 309 air drops before halting the program. Nearly 100,000 people were trapped under the siege.

Pro-government forces broke the siege on September 5 and secured the highway to the capital, Damascus, shortly after. It immediately began organizing its own aid deliveries to the city, replenishing empty store shelves with milk, pasta, canned foods, and other basic goods.

Prices for basic foodstuffs have fallen by 25 to 30 per cent since the final days of the siege, according to Gaziantep-based Ali Rahbe, of the activist-run Justice For Life monitoring group.

The government now controls two-thirds of Deir el-Zour, according to the Britain-based Syrian Observatory for Human Rights monitoring group.

But its campaign has come at a high cost to civilian life, says the Observatory and the activist-run monitoring group, DeirEzzor 24.

Both groups say aircraft have been bombing river crossings, hospitals, and other civilian infrastructure along the Euphrates River Valley. The Observatory reported 34 civilian fatalities since Saturday, attributing four to coalition air strikes on the IS stronghold Mayadeen.

The claims could not be independently verified in real-time. The groups rely on local contacts to smuggle information out of IS-held territory.