Beirut - The extremists of the Islamic State group have turned their social media into a theatre of horror, broadcasting a stomach-turning stream of battles, bombings and beheadings to a global audience.
The strategy is aimed at terrorising opponents at home and winning recruits abroad. But there are increasing signs of pushback - both from companies swiftly censoring objectionable content and users determined not to let it go viral.
Public disgust with the group's callous propaganda tactics was evident following the group's posting of the beheading video of American journalist James Foley - chilling footage that spread rapidly when it appeared online late on Tuesday.
The slickly edited video begins with scenes of US President Barack Obama explaining his decision to order airstrikes in Iraq, before switching to Foley in an orange jumpsuit kneeling in the desert, a black-clad Islamic State fighter by his side.
The fighter who beheads Foley is then seen holding another US journalist, Steven Sotloff, threatening to kill him next. "The life of this American citizen, Obama, depends on your next decision," he says.
Mass slaughter
By Wednesday, many social media users were urging each other not to post the video as a form of protest.
Phillip Smyth, a University of Maryland researcher who tracks the social media activity of jihadists, has noted a modest but noteworthy rise in the speed with which rogue accounts are being removed from Twitter and terror-supporting pages are being pulled from Facebook.
"It's happening," he said. "I can tell you first-hand because I look at this stuff every day."
The Islamic State group, an al-Qaeda offshoot, has been a determined user of social media, broadcasting high-definition video of horrific forms of punishment including crucifixions, beheadings, stonings and mass slaughter.
A chilling, 61-minute video posted online in June, shows Islamic State militants knocking on the door of a Sunni police major in the dead of night in Iraq. When he answers, they blindfold and cuff him before they slice off his head with a knife in his own bedroom.
The fear created by such footage was seen as one factor behind the stunning collapse of Iraqi security forces when Islamic State fighters overran the cities of Mosul and Tikrit in June.
Faysal Itani, a resident fellow at the Atlantic Council, said the militants' slick production techniques are partly due to the foreigners who have joined their cause.
"They're the Twitter generation," he said. "They're good at it."
Vanishing act
Twitter says it's trying to keep the group's most gruesome videos off its platform, an issue that gained new urgency following the release of the Foley beheading footage.
In a tweet, CEO Dick Costolo said his company was "actively suspending accounts as we discover them related to this graphic imagery".
Smyth and others who track such activity reported a steep drop-off in jihadi posts after that. The number of images from Islamic State militants "dropped dramatically", researcher JM Berger said in a tweet, while Smyth said some 50-odd accounts associated with the group had been suspended.
Video-sharing sites saw a similar vanishing act.
On YouTube, which is owned by Google, the images were posted for some time on Tuesday before being removed.
By Wednesday, searches on YouTube mainly turned up links to news reports of Foley's slaying, or to reedited videos that removed footage of the beheading.
In a statement, YouTube said its policies "prohibit content like gratuitous violence", and it removes videos in violation when flagged by users.
Facebook said it began removing links to the Foley beheading on Tuesday, a process that continued on Wednesday as users reported the clips. The California company said it was still allowing people to post snippets of the clip in the context of a discussion about the incident.
James Lewis, a senior fellow at the Washington-based Centre for Strategic and International Studies and director of its strategic technologies programme, said companies acted responsibly in removing the footage fast.
"Taking this stuff down off the social networks is important," he said. "You shouldn't suppress the facts, but you can suppress the image. That's just pornography."