RAQQA, Syria: U.S.-backed fighters Monday combed through a central district of Syria's Raqqa that once housed key Daesh (ISIS) command centers, recovering communication equipment and weapons used by the militants.

The Syrian Democratic Forces have captured around 90 percent of Daesh's one-time bastion Raqqa, including about half of the Al-Nahda neighborhood on the western edge of the city center.

After hard-fought battles against Daesh this week, SDF units on Monday were searching house-by-house for weapons or documents left behind by Daesh.

"This neighborhood was a strategic place for Daesh. Most of their bases were here, including command centers and ammunition depots," local SDF commander Gabar Derek said.

Many of the buildings in the area are large stone complexes formerly used by Syria's government, then taken up as bases by IS before the SDF moved in.

"A few days ago we advanced into a position used by Daesh and found walkie-talkies. We took out a lot but there was a part we could not remove until today," said Derek, 25.

As he spoke, his fighters unloaded an armored vehicle full of dozens of walkie-talkies, military fatigues and boots, a gas mask, rocket-propelled grenades, and even a serrated sword retrieved from the former Daesh command center.

"Walkie-talkies are important so we know what channels Daesh are using to communicate, how they're moving, and what their plans are. We're monitoring them," Derek said, a floral scarf wrapped around his spiky black hair to keep it out of his eyes.

Recent sweeping operations had also uncovered stacks of IS administrative documents, hundreds of mobile phones, a weaponized drone, a tablet computer, and even metal coins branded "the Islamic State" [Daesh].

If the spoils included useful ammunition or military gear, SDF units asked permission to keep them, Derek said.

Fighters on Monday could be seen trying on pairs of beige military boots they had snatched from the Daesh position.

Everything of potential intelligence value was sent up the chain of command to transfer to the appropriate units.

"Even if we find just a needle, we'll send it to the intelligence," Derek added.

Captured by Daesh in 2014, Raqqa became the de facto Syrian capital of the group's notorious "caliphate" and was believed to serve as a major planning hub, including for attacks abroad.

The SDF - an alliance of Kurdish and Arab fighters - are working to tighten the noose on Daesh militants holed up in a part of central Raqqa that includes the national hospital and football stadium.

They are believed to be holding civilians in these facilities with them as human shields.