Islamic State militants kill American journalist on video
The Islamic State (IS) has released a video online purporting to show the beheading of US journalist James Foley, who went missing in Syria in 2012.
The jihadist militant group said the killing was revenge for US air strikes against its fighters in Iraq.
Foley's mother Diane said on Facebook she was proud of her son: "He gave his life trying to expose the world to the suffering of the Syrian people."
The White House said if the video was genuine, the US would be "appalled".
Foley, 40, has reported extensively across the Middle East, working for the US publication GlobalPost and other media outlets including French news agency AFP.
British accent
In the video, titled A Message to America, a man identified as James Foley is dressed in an orange jumpsuit, kneeling in desert-like terrain beside an armed man dressed in black.
He gives a message to his family and links his imminent death to the US government's bombing campaign of IS targets in Iraq.
Clearly under duress, he says: "I call on my friends, family and loved ones to rise up against my real killers, the US government, for what will happen to me is only a result of their complacency and criminality."
Then the masked militant, who speaks with a British accent, delivers a warning to the US government: "You are no longer fighting an insurgency. We are an Islamic Army and a state that has been accepted by a large number of Muslims worldwide.
"So any attempt by you Obama to deny the Muslims their rights of living in safety under the Islamic caliphate will result in the bloodshed of your people."
After he speaks, the militant appears to start cutting at his captive's neck before the video fades to black.
His body is then seen on the ground.
Another captive, identified as American journalist Steven Sotloff, is shown at the end, with the warning that his fate depends on President Barack Obama's next move.
Mr Sotloff was abducted a year ago in northern Syria, close to the border with Turkey.
In a statement, GlobalPost asked for "prayers for Jim and his family", adding that it was waiting for the video to be verified.
UK Prime Minister David Cameron said "if true, the murder of James Foley is shocking and depraved."
Foreign Secretary Philip Hammond acknowledged the militant appeared to be British. The involvement of a significant number of UK nationals in Syria and Iraq was "one of the reasons why this organisation represents such a direct threat to the UK's national security", he told the BBC.
Foley had covered the war in Libya and was detained there for more than 40 days.
