US-backed Syrian fighters captured their first western district of the ISIS group’s bastion Raqqa on Sunday, days after seizing an eastern neighbourhood from the jihadists.

A statement by the Syrian Democratic Forces said their fighters “liberated the neighborhood of Al-Romaniya on the western front of Raqqa, after two days of continued clashes.”

It said the fighting there had left at least 12 ISIS militants dead.

Backed by the US-led coalition bombing ISIS, the SDF's Arab and Kurdish fighters broke through the northwestern district of Al-Romaniya on Saturday.

The alliance is also in control of the eastern neighborhood of Al-Meshleb, which it captured within a day of first entering Raqqa city.

Held by ISIS since 2014, Raqqa emerged as a key hub for the extremist faction’s operations in Syria, neighboring Iraq, and beyond.

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The SDF has spent seven months tightening the noose on the city before finally entering it on Tuesday.

More than 320,000 people have been killed since Syria’s conflict erupted in March 2011 with demonstrations against President Bashar al-Assad.

It has since turned into war pitting extremists, rebel groups, government forces, and Kurdish fighters against each other.