Syrian Democratic Forces breached the Old City of Raqqa after overcoming heavy push back from Islamic State militants Monday, U.S.-led coalition officials said.

The U.S.-backed fighters were able to open up two small gaps in the Rafiqah Wall, which surrounds the Old City. Coalition forces conducted airstrikes on small portions of the wall to help the Syrian Democratic Forces get through ISIS’ prepositioned mines and IEDs, officials said.

Officials added that the U.S.-backed fighters would have been extremely vulnerable without the aid of the airstrikes. The forces faced vehicle-borne IEDs, heavy machine-gun fire and snipers as they moved into the Old City, officials said.

"Unlike ISIS who deliberately destroyed the ruins of Palmyra and the Al-Nuri mosque and uses sites such as the Rafiqa Wall, hospitals, schools and mosques as weapons storage facilities and fighting positions, Coalition forces are making a great effort to protect civilians and preserve these sites for future generations," Coalition spokesman Col. Ryan Dillon said.

The latest advance into Raqqa comes days after the U.S.-backed fighters seized the last road into Raqq and began their trek along a river south of the city Thursday.

The advance toward Raqqa city began last year, as Kurdish-led forces fought to clear rural parts of the province of the presence of ISIS militants.

Backed by airstrikes from the international coalition, the Syrian fighters captured the strategic town of Tabqa in May, and seized one of Syria's major dams that lies nearby. The battle for the city began in earnest on June 6, as the fighters moved in from east, west and north of Raqqa. The fight on the southern front began later this month. Scrocca warned that the fight for Raqqa city has only began.

Dillon said last week that ISIS fighters have been “abandoned” by their leadership as a “steady stream” of leaders attempted to escape the city, some “succesffully.” He said in the last week, the SDF have cleared seven and a half square miles of territory in and around Raqqa.

Fox News’ Jennifer Griffin and the Associated Press contributed to this report.