Raqa (Syria) (AFP) - US-backed fighters battled hundreds of Islamic State group jihadists holed up in the last pockets of Syria's Raqa, as the former extremist stronghold stood on the verge of capture.
Intermittent artillery fire could be heard Monday and thick columns of smoke rose above the devastated city as US-led coalition air strikes targeted remaining jihadists.
"The Syrian Democratic Forces (SDF) are currently waging their toughest battles yet," Jihan Sheikh Ahmed, spokeswoman for the operation to capture the city, told AFP.
The latest fighting "will bring an end to Daesh's presence", she added, using the Arabic acronym for IS.
"They can choose between surrendering and dying."
Only around 300 IS fighters are believed to remain in the devastated city, once the de facto Syrian capital of the jihadist group's self-styled "caliphate" straddling Syria and Iraq.
"The IS elements that are still there are resisting," Sheikh Ahmed said, adding that the fighting was centred on "fortified and heavily mined areas".
The SDF, an alliance of Kurdish and Arab fighters, broke into Raqa in June and captured around 90 percent of it before local officials brokered a deal over the weekend to evacuate remaining civilians.
Overnight, SDF fighters captured the northern Al-Barid neighbourhood, and on Monday they announced they had secured two more adjacent districts.
Inside the city, an AFP reporter saw heavy destruction around the national hospital, one of IS's key remaining positions, though the complex's observation tower was still standing.
- 'Final phase' -
"Our forces are clearing the area, we haven't entered the hospital yet," 22-year-old SDF fighter Shoresh Halab said.
"After the evacuation of civilians, the operation has become easier for us. Daesh was taking the civilians and putting them in front so the planes wouldn't hit them."
On Sunday, the SDF announced the "final phase" of the battle for the city, with a resumption of fighting after a pause to negotiate the safe exit of civilians and the surrender of some IS fighters.
In a statement, the militia said the last phase of the fighting would "end the presence of the terrorist mercenaries inside the city".
"The battle... will continue until the entire city is cleared of terrorists who refuse to surrender, including foreign terrorists."
SDF spokesman Talal Sello told AFP on Sunday that the city was virtually empty of civilians after 3,000 left Saturday as part of a deal agreed between local officials and Syrian IS fighters.
"Only 250 to 300 foreign terrorists who refused the deal and decided to stay and fight until the end remain in the city, and relatives of some members are with them," he said, without specifying the number of civilians.
Under the deal, a total of 275 Syrian IS fighters and relatives surrendered to the SDF, though it was unclear whether they would be given safe passage elsewhere.
In a gutted seven-story building overlooking the city's stadium, a fighter called out for civilians to approach on Monday.
A child's cry could be heard, but it was unclear where the sound was coming from and no one emerged.
Muthanna Shahin, a civilian SDF member, reminisced about childhood football games played at the stadium. "When I see it now, I'm so sad I can't even cry," he said.
A spokesman for the US-led coalition said Monday its strikes had been on hold during talks on the deal to evacuate civilians but the attacks would now resume.
"Now that that arrangement is complete and the SDF are going to resume their offensive into the city I certainly expect that strikes will increase," Colonel Ryan Dillon told AFP.
But he declined to speculate how quickly the city could now fall.
"We still expect that the fight in this final piece is going to be difficult," he said. "We're not putting a timeline on it."
IS captured Raqa in 2014. Under its rule, the city become synonymous with the jihadist group's worst abuses and was transformed into a planning centre for attacks abroad.
The city's recapture would be only the latest blow for IS, which has suffered a string of defeats in recent months.
It was driven from its largest Iraqi stronghold Mosul in July and now only controls a fraction of the self-styled "caliphate" it proclaimed more than three years ago, an area which was once about the size of Britain.
In Syria, its presence is largely confined to the eastern province of Deir Ezzor, where it is under attack by both the SDF and a Russia-backed Syrian government campaign.