The Syrian Democratic Forces (SDF) are being slowed in their battle for al-Raqa by fierce resistance from the "Islamic State of Iraq and Syria" (ISIS), which has heavily mined the city, AFP reported Wednesday (August 9th).

The Arab-Kurd alliance entered al-Raqa two months ago, backed by the coalition, and have since captured more than half of the city, said Operation Wrath of the Euphrates spokeswoman Jihan Sheikh Ahmed.

But the forces' progress has been hindered by ISIS, which is fighting hard to hang on to the Syrian capital of its self-proclaimed "caliphate".

"Our forces are continuing to advance inside al-Raqa, but slowly," Sheikh Ahmed said.

She said SDF forces had seized nine districts in the city's west and east, while ISIS was putting up a fierce defence of the seven remaining neighbourhoods.

"After being besieged from four sides, ISIS has no option but to surrender or die," she said. "That is what has made its reaction fiercer."

ISIS has laid explosives "in every centimetre" of the city, she said, slowing the SDF's progress.

Sheikh Ahmed said the SDF also was facing ISIS snipers and weaponised drones, adding that the group had staged commando-style attacks within territory recently captured by the SDF.

But she said the campaign was progressing "with steady steps, no matter how slow".