Civilians ride a motorbike past an advocacy office that belonged to Islamic State fighters in the town of Tel Abyad, Raqqa governorate, Picture taken June 19, 2015. REUTERS/Rodi Said

Activists in Raqqa, the self-declared capital of ISIS, have established a clever system for countering the spread of Islamic State propaganda, a Sky News documentary uncovered.

Members of the group Raqqa Is Being Silently Slaughtered (RBSS) are leaving copies of their anti-ISIS magazine across the city. However each copy is disguised by being printed with the front cover of Islamic State's own propaganda publication.

The trick has been so successful that the magazines have been able to spread across Raqqa under the noses of Islamic State fighters.

Abdulaziz Alhamza, co-founder of RBSS, told Sky News in an interview: "We have a magazine that we spread through the city.

"Our magazine cover is the same as the Islamic State magazine cover so when we spread it in the streets even ISIS fighters and members think it's their own magazine.

"When they open it they find our ideas and our material. By this magazine we are trying to focus on children because right now we are not only fighting ISIS but the ideology of extremism."

RBSS is a small group of citizen journalists dedicated to exposing the realities of life in Raqqa under the rule of Islamic State.

The activists use YouTube and social media to reach a global audience but on the ground are coming up with bold means of resisting ISIS, also known as IS, ISIL, and Daesh.

RBSS members also put up posters and spray graffiti on city walls in an attempt to spread an anti-ISIS message and protect the city's children from indoctrination.

Fighters from Islamic State burn confiscated cigarettes in the city of Raqqa, April 2, 2014. REUTERS/Stringer

Children as young as eight are thought to be on the front line fighting for ISIS and RBSS activists say that future generations of Syrians must be protected if the terrorist group is to be defeated.

"There are a lot of suicide bombers that Daesh (IS) have orchestrated — as well as brainwashing the children," fellow co-founder Sarmad al Jilane told Sky.

"They place them in the front line of battles and if they are killed then they are considered to be protecting Daesh lives."

"Those kids are a whole generation that's lost."