ISIS fighters ride horses during a parade in Raqqa, Syria.
ISIS fighters ride horses as they take part in a military parade along the streets of Syria's northern Raqqa province June 30, 2014. REUTERS/Stringer

Hundreds of U.S. Marine Corps troops have been deployed in Syria to fight the Islamic State group, also known as ISIS, the U.S.-led coalition confirmed Thursday.

"We are talking about an additional 400 or so forces in total, and they will be there for a temporary period," the coalition spokesman U.S. Air Force Colonel John Dorrian told Reuters.

The forces — a Marines artillery unit and Army Rangers — arrived in the “last few days,” Dorrian reportedly said. The troops will work with local alliances in Syria, including the Syrian Democratic Forces and the Syrian Arab Coalition, he said, adding, the forces will not be given a frontline task.

On Wednesday, the Washington Post was the first to report, citing defense officials, about the deployment. The forces are part of an amphibious task force of the 11th U.S. Marine Expeditionary Unit that San Diego on navy ships in last October, according to the report. The deployment also includes a part of an artillery battery that can fire 155-millimeter shells from M777 Howitzers.

A defense official told the Post that the decision to deploy Marines in Syria was due to President Donald Trump’s plan to fight ISIS. Instead it was “been in the works for sometime,” the official said.

“The Marines answer a problem that the [operation] has faced,” the official said. He added that they now provide “all-weather fires considering how the weather is this time of year in northern Syria.”

Raqqa reportedly has 3,000 to 4,000 ISIS fighters. However, the militant group’s leaders have been fleeing the city in recent months due to the U.S.-coalition fight.

"Raqqa will probably not be the final battle against ISIS," a U.S. official reportedly said Wednesday, adding that the group is likely to have some militants spread in areas south and east of the city.