RBSS is made up of a small number of people still living in Raqqa who send out pictures and information from inside the besieged city.
Their work is key to gauging an idea of what life is like under Isis, as only a few journalists have managed to enter Raqqa and leave safely.
The extremist group has committed a spate of atrocities since it advanced across Syria and Iraq as it try to establish a "caliphate", including the beheading of hostages and the death of a Jordanian pilot it burned alive.
In December, Isis published a copy of its penal code and vowed to strictly enforce it in areas under its control.
Punishments for acts it deemed criminal included stoning to death, crucifixion and amputation.
- Independent