A member of the Syrian Democratic Forces (SDF) crosses a street on June 27, 2017 in the suburb of Dariya on the western city limits of Raqqa after the area was seized by SDF from the ISIS.

:: US-backed forces in Syria have breached the wall surrounding the Old City of Raqqa as they try to retake the city from ISIS, the US Central Command said Monday night.

“Coalition forces supported the SDF advance into the most heavily fortified portion of Raqqa by opening two small gaps in the Rafiqah Wall that surrounds the Old City,” Centcom said in a statement, referring to the Syrian Democratic Forces.

US-backed fighters pierced militant-held Raqqa from the south for the first time on Sunday, crossing the Euphrates River to enter a new part of the Syrian city, a monitor said.

The Syrian Democratic Forces have spent months closing in on the ISIS bastion and entered the city’s east and west for the first time last month.

Centcom said the SDF faced heavy resistance at the wall from ISIS fighters who used it as a combat position and planted mines and improvised explosive devices against advancing US-backed soldiers.

“Conducting targeted strikes on two small portions of the wall allowed coalition and partner forces to breach the Old City at a locations of their choosing, denied ISIS the ability to use pre-positioned mines, IED and VBIEDs, protected SDF and civilian lives, and preserved the integrity of the greatest portion of the wall,” the US statement said.

“The portions targeted were 25-meter sections and will help preserve the remainder of the overall 2,500-meter wall,” it added. According to the coalition, an estimated 2,500 ISIS militants are defending the northern city.

ISIS overran Raqqa in 2014, transforming it into the de facto Syrian capital of its self-declared “caliphate,” which it declared three years ago.

The city became infamous as the scene of some of the group’s worst atrocities, including public beheadings, and is thought to have been a hub for planning attacks overseas.

The United Nations has expressed concern for up to 100,000 civilians it says are still trapped in the city.