Supporters of the Islamic State are "reveling" in a video appearing to show the beheading of a US journalist, a jihadism expert has told ITV News.
"For the ordinary members of the public this video is brutal; it's shocking; it's really inexplicable....but to those who are supporting the Islamic State they are reveling in this," Shiraz Maher said.
"There is a lot of chatter online where they are supporting this because for them they will enjoy anything that is a challenge to the United States or that humiliates the United State."
Mr Maher said the number of British men joining IS militants fighting in Syria and Iraq shows no sign of falling, as the declaration of a caliphate in IS-held areas had "galvanised" supporters.
Maher suggested it was was unlikely British militants would want to leave the Islamic State to resettle in the UK, with the kidnappings of western individuals and the targeting of British or American interests in the Middle East more likely.
A British family have told ITV News of their devastation after discovering a close relative is fighting with the Islamic State in Iraq.
A French journalist who was held hostage with James Foley in Syria has told ITV News it was "devastating" to see his murder.