The Syrian Observatory for Human Rights on Wednesday said the aircraft landed in the vicinity of the town of Hajin, one of the last IS-held towns in the eastern countryside of Deir al-Zour, Xinhua news agency reported.
It said the Marine forces will participate in the battle alongside the Syrian Democratic Forces (SDF) against IS militants.
According to the London-based watchdog, the US move aims to intensify the anti-IS military campaign on the eastern bank of Euphrates River.
Since the battle was launched on September 10, the IS militants have been well fortified with landmines and suicide bombings, leading to slow advance of the Kurdish-led SDF backed by the US-led airstrikes.
The pro-rebel monitor also said 211 IS militants, along with 113 SDF fighters and allied militiamen, have been killed in the fighting since September 10.
The Syrian army has cleared the IS from large swathes of areas in Deir al-Zour, while the SDF is attempting to consolidate positions in the northern and northeastern countryside of the province.
Recent reports said the IS-controlled Syrian territory has shrunk to one per cent from almost half of the country a couple of years ago.
The Syrian government has slammed these operations in Syria as "illegal" since the US-led coalition entered the Syrian war in 2014, saying the United States has been trying to establish presence in eastern Syria through supporting the Kurdish-led SDF, in order to secure its interests in the country.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
