They started arriving five days ago, the source said. In addition to several hundred US marines, an artillery battery is expected to arrived from the Iraqi base.
According to the source, part of the military forces, which cannot arrive in Syria using helicopters, will be transported by land through the Semalika passage located between Syria and Iraqi Kurdistan.
"The number of the US forces which are currently in Syria has been boosted under the Barack Obama administration. Earlier, their presence was limited to military experts and advisors, while now we witness the arrival of the Marine Corps forces," the source told Sputnik.
The United States deployed US marines to the Syrian city of Raqqa without the permission of the Damascus government, Central Command chief Gen. Joseph Votel said earlier. He said that US Marines have been deployed to Syria to make sure coalition troops on the ground receive necessary support in the fight to retake Raqqa from the Daesh.
The marines will be supporting US partner forces on the ground that lead the offensive to liberate Raqqa from Daesh codenamed Operation Euphrates Rage. The operation was launched by the Kurdish-led Syrian Democratic Forces (SDF) on November 5, 2016. The SDF was formed in 2015 as the defense force of northern Syria's de facto autonomous Rojava federation and is supported by the US-led coalition. The group is among the forces fighting Daesh and brings together Kurdish, Arab, Assyrian and Turkmen fighters, among others.
The news comes after the Pentagon was tasked to send US President Donald Trump options to accelerate the fight against Daesh.