(CNN) The streets are eerily empty, with few signs of life in sight. Plumes of smoke billow from the top floors of hollowed out buildings. Neighboring structures appear flattened by mortars and bombs.

This is Raqqa, the capital of ISIS' caliphate in Syria, and the terror group's last major stronghold

SDF forces advance through west Raqqa, where the threat of ISIS snipers is never far.

Photojournalist Gabriel Chaim has captured drone footage and photographs while embedded with the Syrian Democratic Forces -- part of the US-led offensive -- that give a rare look inside the city.

For the past three years, access to Raqqa has been extremely limited -- only smuggled videos and occasional satellite footage have provided a glimpse into the besieged city. Under ISIS' brutal regime, phones and cameras were banned and anyone caught with videos or images could have faced death.

Even with parts of Raqqa liberated from ISIS control, photographing the city is still risky.

Raqqa's remaining civilians -- up to 20,000 people, according to the SDF -- are trapped in their homes, fearful of fleeing because of snipers, air raids and street battles, according to SDF commander Haval Zargos.

In July, the UN estimated between 30,000 and 50,000 people were trapped in Raqqa, noting the difficulty in pinpointing exact numbers because of the difficulty of access.

Speaking to CNN from Raqqa's front line, Zargos estimates that around 1,500 ISIS militants remain inside the city, using an elaborate labyrinth of mines and civilians as human shields to stop coalition forces from advancing at speed.

A SDF sniper targets Isis fighters in west Raqqa on August 25.

"They have mines planted everywhere throughout the neighborhoods, so we have to clear every residence while we face occasional sniper fire," Zargos said, adding that the group is also using car bombs.

Photojournalist Chaim said ISIS is also using drones to halt the SDF from advancing closer to the city center. He told CNN he narrowly avoided injury when an ISIS drone exploded meters from a SDF vehicle he was embedded in.

SDF forces monitor an ISIS drone hovering near the front line on Saturday.

Chaim's aerial footage shows Raqqa's paths and streets nearly empty, with less than a handful of SDF soldiers patrolling them in the bright sun.

During the day, they carry out demining operations, moving with extreme caution because of the risk of ISIS snipers. From dusk, they navigate through Raqqa's east and southeastern neighborhoods -- areas where fighting has intensified in recent weeks.

Local residents refuel at an improvised gas station in a liberated area in west Raqqa on Friday.

Even in the west, where the SDF has held large areas for nearly a month, coalition forces say they still face sniper fire, mines, and car bombs.

When the clashes inside the city are at their most intense, SDF forces send word to coalition forces who respond from the air -- sometimes carrying out up to 20 airstrikes a day, according to Zargos.

The bombings have helped coalition troops advance, but many civilians have been killed in the strikes.

The SDF says the front line is currently located around just one kilometer from the city center. Two months after it began, the battle is far from over.