US-backed forces captured a new district from ISIL in Raqqa but were struggling to hold their positions against suicide car bombers in the northern Syrian city on Friday.
The Syrian Democratic Forces, an alliance of Kurdish and Arab fighters, seized the eastern Batani district from ISIL on Thursday.
"Late Thursday, they began an offensive on neighbouring Al Rumeilah," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, a Britain-based monitoring group.
Clashes were raging on Friday as ISIL deployed its typical defensive tactics: weaponised drones, snipers, and improvised explosive devices, Mr Abdel Rahman said.
An SDF fighter near Al Rumeilah said ISIL was using suicide bombers to try to stop their advance
"They're sending booby-trapped cars towards our positions, and as they fall back, they're laying mines," said the 30-year-old fighter, who identified himself as Abu.
Civilians "can't move. They can't leave during the day because of snipers."
Abu said his unit had managed to open up an escape route for residents of Al Rumeilah, like 56-year-old Abdel Halim Ulaywi.
"Ten days ago, a strike hit our home and we ran inside quickly. My sister was hit in the stomach and started bleeding. She stayed alive for six days and then she died," Mr Ulaywi said.
He had tried to escape several times "but ISIL kept forcing us back".
Mr Abdel Rahman said ISIL has slowed down the SDF's push in other parts of Raqqa, including the Old City.
"The SDF is struggling to hold newly seized positions in the Old City because of intense sniping and escalating attacks by drones carrying bombs," he said.
ISIL captured Raqa in early 2014, transforming the northern Syrian city into the scene of gruesome atrocities such as public beheadings.
The SDF, backed by US-led coalition air strikes, spent months encircling the city before finally breaking into it on June 6.
The militia has since captured about 30 per cent of the city.
