From online videos to the social network postings of their fighters, the propaganda of the Islamic State jihadist group is evolving to prevent the leaking of strategic information while at the same time maintaining its impact.
Experts and journalists say they have observed a change in the group's approach to communications since its offensive on the Syrian town of Kobane and air strikes by a US-led coalition.
After making extensive use of social networks and different Internet platforms to publicise their activities, IS seems to have realised that some of the images being posted by their fighters could also be used against them by foreign intelligence services.
Abdelasiem El Difraoui, author of "Al-Qaida par l'image" ("Al-Qaeda through images") and an expert in radical Islam, told AFP the group had responded to the potential dangers created by this earlier strategy.
"The social networks helped greatly with recruitment. (But) as soon as this put operational security in danger, they tightened up," he said, adding that many of its recruits were Westerners who were confident social media users.
David Thomson, a French journalist and author of the book "The French Jihadists", said that before the intervention of the coalition the publication of photos taken by IS fighters had been positively encouraged.
"The instruction was to 'show a positive image of us' in order to push immigration and facilitate recruitment," he said.
The jihadist group launched an offensive against Kobane, near the Turkish border, last month as it sought to expand its control over large parts of Syria and Iraq where it declared an Islamic "caliphate" earlier this year.
But Thomson said that at the start of the offensive, what appeared to be an internal IS document had asked fighters not to film or take photographs with their mobile phones any more.
The instruction was applied with "varying degrees of rigour" and had not stopped some from continuing to post "photos or selfies", he said.
- Propaganda strategy -
The shift in IS's propaganda strategy was also discernible in the videos put on the Internet and aimed at the media, according to Henry Bouvier, a senior editor at Agence France-Presse's video service.
"We feel that the jihadists are evolving in the way that they are communicating. They are adapting to the media's needs," he said.
With the areas controlled by IS inaccessible to journalists, AFP uses selected images shot and put on line by the group and its affiliates in order to transmit them to other media.
Celine Pigalle, director of information at the French television group Canal+ noted recently that IS's images appeared to have been "produced by a specialist agency" with "great professionalism".
AFP uses such images only after careful consideration of each one.
Most of the media, including AFP, has refused to broadcast recent videos showing the beheading of journalists James Foley and Steven Sotloff, aid worker David Haines and humanitarian convoy volunteer Alan Henning.
"They (IS) are well aware that to be picked up they must respect certain codes. More and more, when they can, they show car licence plates or identifiable places, such as the Kobane cultural centre" in order to allow the media to authenticate the images, Bouvier said.
"They shoot images TV-style, without music or special effects. Even in the way they present people or speak, they are more neutral and more journalistic," he added.