US-backed Syrian fighters ousted the Islamic State group from Raqa's Old City on Friday, bringing them closer than ever to the jihadist bastion's well-defended and densely populated heart.
Backed by US-led coalition air strikes, the Syrian Democratic Forces first broke into Raqa in early June and penetrated its Old City a month later.
On Friday, they successfully captured the entire historic district from jihadists.
"Our forces today seized full control of the Old City in Raqa after clashes with Daesh," spokesman Talal Sello said, using the Arabic acronym for IS.
"We are on the edges of IS's security quarter in the city centre, where most of its main bases are."
SDF forces are in control of neighbourhoods across Raqa's south, west and east -- constituting more than 60 percent of the city. 
IS, in turn, holds part of the north and centre, where up to 25,000 civilians are estimated to still be trapped. 
IS's prized "security quarter" lies directly west of the Old City and is home to buildings formerly used by Syria's government but now taken up as bases by IS.
The Syrian Observatory for Human Rights, a Britain-based monitoring group, said the SDF was still locked in clashes with IS in a small part of the Old City on Friday.
Observatory head Rami Abdel Rahman said that around 1,000 jihadists were still left in the whole city.
- 'Sigh of relief' -
IS overran Raqa in 2014, turning it into the de facto capital of its self-declared "caliphate".
The city was the scene of some of the group's worst atrocities, including public beheadings.
The SDF advanced into the Old City two months ago by breaching the Rafiqah Wall, a 2.5-kilometre (one-and-a-half-mile) wall surrounding the district.
US-led coalition air strikes had opened up two breaches in the wall, which dates back to the late 8th century when Raqa was briefly the centre of the Islamic world.
"Control over the Old City -- which has historical importance -- is a moral victory against IS, which is collapsing in Raqa. Its defeat there is inevitable," Sello told AFP.
He declined to say when the alliance expected to seize all of Raqa, but said operations were proceeding "according to schedule".
Syria's antiquities chief Maamoun Abdulkarim told AFP on Friday that he "breathed a sigh of relief" when he learned that IS had been ousted from the Old City.
"Raqa was one of the Abbasid capitals and it means a lot to us. The end of Daesh there would mean the protection of Syrian cultural heritage in an historically important city," he said.
Despite the damage, Abdulkarim said he was reassured that the Rafiqah Wall remained mostly intact and could be restored.
"We didn't lose the most important historical element of the Old City. The wall is the symbol of the city."
The SDF's advance is the latest in a string of setbacks for IS, both in Syria and in neighbouring Iraq.
In Syria's east, Russian-backed government troops are pushing steadily into the oil-rich province of Deir Ezzor, where IS still holds key territory.
In Iraq, soldiers recaptured the northern city of Tal Afar and the surrounding region from IS on Thursday, just two months after defeating the jihadists in second city Mosul.
The fall of Tal Afar, located in the northern province of Nineveh, deprives IS of what was once a key supply hub between its territory in Iraq and neighbouring Syria.