The plight of the Syrian city of Raqqa, the “capital” of the so-called Islamic State is rarely out of the news. Matthew Heineman’s exceptional, award-winning documentary examines, with unflinching intimacy, the power and resolve of grassroots journalism in the midst of this war against terror and twisted ideology.

City of Ghosts tells the story of RBSS (Raqqa is Being Slaughtered Silently), a small group of extraordinarily brave Syrian citizen journalists who risk their lives to document and expose the realities of life in their once “simple” city that was taken over by Isis in 2014.

Since its establishment, RBSS has been a vital source of video and photographic images and written testimony about the horrors of Isis rule. The group, made up of young, previously apolitical men — none of whom had been a journalist before — maximises social media to transmit its message. The approach is less a war fought with guns and more a battle waged with laptops and mobile phones.

But City of Ghosts is not a detached recounting of brave activism. Heineman has clearly gained the members’ trust and this personal access and the men’s candour makes the film compassionate and compulsive viewing.

Much of the film takes place in Germany and Turkey using fly-on-the-wall reportage, often from smoke-filled safe houses as the founders have been forced to flee into exile, their names on Isis death lists. Although Heineman shows the strength of brotherhood, he also portrays suffering, trauma and tragedy on unimaginable levels. Several members and friends of the group are hunted down, captured and killed. Co-founder, Hamoud, watches an Isis propaganda video of his father’s assassination, arrested and shot when his killers were unable to find Hamoud himself. He later learns, too, of his brother’s fate — another murder because of association.

At one point, Isis removes satellite dishes and cuts the internet in Raqqa, in an attempt to prevent its clandestine news footage getting out. The portrayal of unimaginable violence and challenges to daily life on the ground is in stark contrast to Isis’s high production value recruitment videos, which mendaciously convey a fully functioning and wealthy country looking to inspire devotion from its people, even from the very young.

City of Ghosts can be difficult to watch but Heineman injects brief moments of relative normality and hope; following former teacher, Mohamad, as he tries to settle into a new home with his wife, and also the birth of Hamoud’s son.

This timely documentary is a stirring testament to courageous journalism and the virtue of and sacrifice for truth, in a world where such values are dangerously undermined. It is essential viewing.