DAMASCUS, Nov. 3 (Xinhua) -- The U.S.-led coalition on Saturday heavily struck areas controlled by the Islamic State (IS) in Syria's eastern province of Deir al-Zour, a war monitor reported.

The airstrikes are coupled with the amassing of forces by the Kurdish-led Syrian Democratic Forces (SDF) around the IS-held pocket on the eastern side of Euphrates River in the eastern countryside of Deir al-Zour.

The Syrian Observatory for Human Rights said 100 special SDF forces arrived at the frontline with IS around its last pocket, and with the latest arrivals, the SDF would have amassed 1,100 fighters so far.

The reinforcement and heavy airstrikes came days after the SDF lost its first wave of attack against the IS pocket as the terror-designated group managed to foil the months-long attack and retake all fallen areas.

Now, the SDF is bringing in special forces of its fighters, who had fought IS in the Raqqa province, which was the de facto capital of the terror-labeled group before losing it in 2017 to the Kurdish-led SDF and the U.S. coalition.

Since the start of first wave of attack on Sept. 10, 516 IS militants as well as 315 SDF fighters have been killed, said the Observatory.

The fresh heavy strikes by the U.S. coalition Saturday comes as the SDF has recently been subject to Turkish shelling, as Ankara seemed determined to launch an offensive against the Kurds in the eastern Euphrates.

A day earlier, the Observatory said the U.S. has 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.