The source said after the coalition's pounding of the Syrian army near Deir Ezzor airbase, the ISIS could take full control of al-Tharda mountain and then Deir Ezzor military base, adding that the army and national defense forces deployed near the airbase immediately won it back from the terrorists by launching a counterattack.

Noting that Deir Ezzor is now almost in tranquility and no change has occurred in the military map of the region, the source said by attacking the Syrian army positions, the US seeks to prevent military operations to break the terrorists' siege on the city.

The source said the simultaneous raid of the ISIL terrorists immediately after the coalition airstrikes is the best evidence of the high coordination done between the US and the terrorists.

Russian Defense Ministry said on Saturday that four strikes against Syrian positions had been delivered by US-led coalition aircraft, including two F-16 jet fighters and two A-10 support aircraft.

The Syrian military called the bombing a "serious and blatant aggression" against Syrian forces, and said it was "conclusive evidence" that the US and its allies support ISIL militants.

Also on Sunday, the Russian foreign ministry spokeswoman blasted Washington over the recent airstrikes near Deir Ezzor, and said such moves serves the interests of the ISIS terror group.

"If previously we had suspicions that Fatah al-Sham Front (formerly known as al-Nusra Front) is protected this way, now, after Saturday airstrikes on the Syrian army we come to a really terrifying conclusion for the entire world: The White House is defending the ISIL," Maria Zakharova said.

"We demand a full and detailed explanation from Washington. That explanation must be given at the UN Security Council," she added.

Russia has demanded full and detailed explanation from Washington over the incident in Deir Ezzor, in which 62 Syrian troops were killed and over 100 injured.

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