Britain said on Saturday it planned tougher laws to deal with British Islamist militants after Islamic State (IS) fighters in the Middle East released a video showing a suspected Briton beheading U.S. journalist James Foley.

British Muslims and politicians have expressed horror at the apparent involvement of a Briton in the murder, which has fed concerns about the number of Islamist militants from Britain joining conflicts overseas and then returning home radicalized.

Authorities are trying to identify the man with a London accent who has been dubbed "Jihadi John" by media after sources said he was one of three Britons nicknamed the "Beatles" who guarded hostages in Raqqa, the IS stronghold in eastern Syria.