MICHAEL BRISSENDEN: The US president has delivered a passionate
condemnation of the killing of James Foley, describing it as a brutal "murder".
Barack Obama has called the reporter's parents to offer his condolences and
The man who killed the reporter spoke with a British accent, prompting British prime minister David Cameron to offer increased efforts to stop his citizens joining the terror group.
North America correspondent Michael Vincent reports.
MICHAEL VINCENT: The US president began his day by calling the Foley family. He told them we are all heartbroken at his death.
BARACK OBAMA: Jim was taken from us in an act of violence that shocks the conscience of the entire world. He was 40 years old, one of five siblings, the son of a mom and dad who worked tirelessly for his release.
MICHAEL VINCENT: Just after midday Barack Obama broke from his family holiday to deliver a four minute statement to the nation, praising the work of James Foley and condemning utterly the actions and motives of his captors.
BARACK OBAMA: They've murdered Muslims, both Sunni and Shia, by the thousands. They target Christians and religious minorities, driving them from their homes, murdering them when they can for no other reason than they practice a different religion. They declare their ambition to commit genocide against an ancient people.
So ISIL (State of Iraq and the Levant) speaks for no religion. Their victims are overwhelmingly Muslim. And no faith teaches people to massacre innocents. No just God would stand for what they did yesterday and what they do every single day.
MICHAEL VINCENT: The beheading of James Foley has reverberated around the United States.
It's brought back memories of other executions like journalist Daniel Pearl in 2002. One former deputy CIA director has called for yesterday's date to be marked as the first act of terrorism by Islamic State directly against the US.
The president says America will seek justice against the militants.
BARACK OBAMA: And people like this ultimately fail. They fail because the future is won by those who build and not destroy and the world is shaped by people like Jim Foley and the overwhelming majority of humanity who are appalled by those who killed him.
The United States of America will continue to do what we must do to protect our people. We will be vigilant and we will be relentless. When people harm Americans anywhere we do what's necessary to see that justice is done and we act against ISIL standing alongside others.
MICHAEL VINCENT: The British prime minister has returned from his holiday to head up emergency security talks to discuss the killing. David Cameron says it is likely the executioner was British.
DAVID CAMERON: We know that far too many British citizens have travelled to Iraq and travelled to Syria to take part in extremism and violence. And what we must do is redouble all our efforts to stop people going, to take away the passports of those contemplating travel, to arrest and prosecute those that take part in this extremism and violence, to take extremism, extremist material off the internet and do everything we can to keep our people safe.
MICHAEL VINCENT: So far the UK has ruled out undertaking military action in Iraq. British leader David Cameron's been asked would this execution prompt a change in policy to attack the Islamic militants on the ground.
DAVID CAMERON: We will stick to the very clear foreign policy and the very clear strategy that we have which is to work with the new Iraqi government, to help make sure the Kurds get the arms they need to fight off these brutal extremist militants, to work with our allies and as I've said, to use everything that we have, our aid, our diplomacy and our military prowess to make sure that with allies, we do everything we can to put the pressure on Islamic State, this appalling organisation and everything we can back here at home to keep our country safe. That is what we must do.
MICHAEL VINCENT: The US State Department's been asked about the remaining captives. It says it's aware other Americans are being held but it's not giving a number for their security.
State Department spokeswoman Marie Harf has said the president will raise the issue of Islamic State recruiting foreigners with world leaders at the UN next month.
This is Michael Vincent in Washington for AM.