DAMASCUS, Nov. 22 (Xinhua) -- The Islamic State (IS) militant group launched on Thursday a large-scale offensive on the positions of the U.S.-backed forces in eastern Syria, as part of its pre-emptive strategy, a war monitor reported.
The IS militants launched the offensive in the morning, trying to reach the al-Tanak oil field, where the U.S.-backed Syrian Democratic Forces (SDF) has a base with foreign military experts, according to the Syrian Observatory for Human Rights.
The London-based watchdog said the IS attack was launched from three directions in an attempt to besiege the positions of the Kurdish-led SDF in the eastern countryside of Deir al-Zour Province.
The assailants detonated two car bombs, leading to the retreat of the first defense line of the SDF on the eastern bank of Euphrates River.
During the battles, the U.S.-led coalition warplanes scrambled and struck the IS positions.
The airstrikes, however, did not last long in the morning because of the foggy weather, said the Observatory.
The U.S.-led airstrikes continued in the afternoon when the weather turned better, which eventually pushed the IS back.
It was the most violent counter-attack from IS militants since the SDF launched an offensive to liberate eastern Euphrates from the IS on Sept. 10, killing at least three SDF fighters and 17 IS militants, according to the monitor.
The IS launched the preemptive attack ahead of the anticipated wide-scale offensive by the SDF on the last IS-held pocket in the eastern Euphrates, it noted.
