London, Washington- United States military advisers are operating inside the city of Raqqa, ISIS’ last major bastion in Syria, a US military spokesman said Wednesday.

The troops, many of them special operations forces, are working in an “advise, assist and accompany” role to support local fighters from the Syrian Democratic Forces as they battle ISIS, said Colonel Ryan Dillon.

The troops are not in a direct combat role but are calling in air strikes and are working closer to the fight than did US forces supporting the Iraqi military in Mosul.

“They are much more exposed to enemy contact than those in Iraq,” Agence France Presse quoted Dillon as saying.

He said the numbers of US forces in Raqqa were “not hundreds” and that they had been working closely with SDF fighters since operations to encircle Raqqa began. 

After months of capturing villages and surrounding terrain, operations to liberate Raqqa started in November and on June 6 the SDF entered the city.

With help from the US-led coalition, the SDF this month breached an ancient wall by Raqqa’s Old City, where diehard militants are making a last stand.

The SDF is a Kurdish-Arab alliance that is being trained by coalition experts and armed by the United States.

Dillon said the coalition had seen ISIS increasingly using commercial drones that have been rigged with explosives. The jihadists employed a similar tactic in Mosul.

“Over the course of the last week or two, it has increased as we’ve continued to push in closer inside of Raqqa city center,” he said.

The Syrian Observatory for Human Rights said Wednesday that the Raqqa city battle, which is taking place for the 37th consecutive day, has allowed the SDF to impose its control over 50 percent of the area of the Old City.

About 730 civilians and fighters were killed in Raqqa city and about third of them are Syrian civilians, it added.