YouTube has said it will terminate any account used to promote the ideology of terrorism, as social media users were urged to stop sharing a video appearing to show the murder of James Foley.
Twitter's chief executive earlier said the site will suspend any user found to be posting graphic images linked to the journalist's death.
YouTube has clear policies that prohibit content like gratuitous violence, hate speech and incitement to commit violent acts, and we remove videos violating these policies when flagged by our users. We also terminate any account registered by a member of a designated foreign terrorist organisation and used in an official capacity to further its interests.
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.