The self-proclaimed Islamic State (IS) has severely restricted use of the internet in its de-facto capital of Raqqa, requiring that all residents — including those in the militant group's ranks — access the web from observed internet cafes, according to international monitoring organizations.

An IS leaflet photographed and circulated by the Syrian Observatory for Human Rights and the activist group Raqqa is Being Slaughtered Silently (RBSS), advises that "all owners of shops with satellite internet must comply with the following: Removing Wi-Fi boosters in internet cafés as well as private wireless adaptors, even for soldiers of the Islamic State."

IS, also referred to as ISIS, has been increasing its control in Raqqa since the summer of 2013, and in January 2014 the extremist group overran a Syrian army garrison and took control of the entire city. Since September 2014, the US and its allies have been pummeling IS positions in the city in a bombing campaign.

Activists worry that internet restriction is intended to clamp down on citizen journalists, human rights workers, and potential IS defectors.

Even under IS rule, activists have managed to sneak out videos, images, and accounts of daily life. In September, a woman with a camera hidden in her niqab walked through the city narrating her experience. The smuggled footage was aired on French TV.

Activists see the new rules as a way for IS to prevent those sorts of leaks in the future. "This step is part of the organization's attempt to impose a news blackout on what is going on inside Raqqa city," the UK-based Syrian Observatory for Human Rights said in a statement. "It has been conducting patrols and raids on internet cafes, searching them for people who are transmitting news."

IS is also "trying to cut communications between its non-Syrian fighters and their families, for fear of them trying to return home," it added.

The restriction could be especially hard on RBSS, which regularly smuggled footage and pictures out of the IS controlled capital and maintains a website and Twitter page which are updated daily.

Speaking to VICE News in 2014, RBSS activist Abu Ibrahim Raqqawi said that even though the internet was one of the few outlets to move information out of the city, avoiding IS detection was a challenge.

"The internet in the city is very, very slow, " he said. "We use internet cafes, and it's very dangerous because ISIS monitors all the internet cafes. So we are risking our lives when we are taking photos of executions with our cell phones."