US-backed Syrian forces set sights on valley north of Raqqa

US-backed Syrian Kurdish forces say they have entered the fourth stage of their campaign to capture the Islamic State group's de facto capital Raqqa with an advance on the militants in a valley north of the city.
The Syrian Democratic Forces, which include Arab fighters, say they are working to clear the militants out of the Jalab Valley, north of Raqqa. An estimated 300,000 people are in the city.
The SDF says it wants to isolate Raqqa before attacking it. Their closest position is within 8 kilometers northeast of the city. But the countryside south of Raqqa is still under IS control.

It is unclear how many stages are planned for the SDF campaign.