US-backed Syrian forces have advanced into the western part of so-called Islamic State’s “capital” of Raqqa, they and a monitor report.

The Syrian Democratic Forces (SDF) said the move had opened up a second front inside the Syrian city. They entered the eastern part earlier this week.

Its fighters were engaged in fierce clashes with the jihadists, it said.

The SDF, supported by US-led coalition air strikes, has spent months encircling the city.