DAMASCUS, Nov. 4 (Xinhua) -- The Islamic State (IS) on Sunday killed and wounded 32 U.S.-backed Syrian Democratic Forces (SDF) fighters during an offensive in eastern Syria, a war monitor reported.

Taking advantage of the bad weather, the IS launched a "violent attack" on the SDF fighters who were poised to launch second wave of battles against the last IS-held pocket in eastern Syria, said the Syrian Observatory for Human Rights.

The Britain-based watchdog group said that the IS attacked the positions of the SDF in the al-Bahra area near the town of Hajin, one of the IS-held towns on the eastern bank of the Euphrates River in the eastern countryside of Deir al-Zour province.

The attack led to the advance of IS in that area and the retreat of the first defense line of the SDF as the attack was surprising, according to the Observatory.

The attack started with suicide bombings and the U.S.-led coalition attempted to provide aerial support to the SDF by striking the advancing IS militants in the area.

Ten U.S. armored vehicles also took part in confronting the IS attack, said the Observatory, adding that the U.S.-led airstrikes couldn't do much because of the intensity of fog.

Earlier in the day, the Observatory said that 14 people were killed by the U.S.-led airstrikes.

Meanwhile, the battles on the eastern bank of the Euphrates are still ongoing after the advance of the IS and the coalition is still shelling the area to force the terror-labeled group to retreat.

The attack of IS on Sunday came as the SDF was amassing forces to conduct another round of battles to defeat IS in its last strongholds in eastern Syria after a failed first attempt that started on Sept. 10.

It also came as the Turkish forces were shelling the SDF positions on the eastern side of Euphrates River as Ankara made it clear that it wants to defeat the SDF as this group is led by the Kurdish People's Protection Units.

Earlier in the day, the Observatory said that the Turkish intelligence moved 700 Syrian rebels from areas in the countryside of Aleppo in northern Syria to areas near the eastern Euphrates.

The Turkish stance reflected the desire to defeat the Kurdish militia in the eastern Euphrates after they had already pushed them to retreat from the western side of the river in two cross-border operations in 2016 and 2018.

On Friday, the U.S. deployed forces along the line separating the eastern part of the Euphrates, where the SDF is located, from the Turkish-backed rebels on the western bank of the river to avert any confrontation.