Cameron 'shocked' that Briton likely involved in Foley's beheading

London - Prime Minister David Cameron said he was shocked that a British citizen looked likely to be involved in a video purportedly showing the beheading of a US journalist James Foley by Islamic State militants, but added that the man had not been identified.

"We have not identified the individual responsible on the video but from what we've seen it looks increasingly likely that it is a British citizen. Now this is deeply shocking," Cameron told broadcasters on Wednesday.

According to AFP Cameron, who broke off his holidays to return to London for meetings on the threat posed by Islamic State militants operating in Iraq and Syria, said "far too many" Britons had travelled to the region to take part in extremism.

He condemned Foley's killing as "brutal and barbaric" and "murder without any justification".