Obama: US will do what it must to protect its citizens
US President Barack Obama has affirmed that the beheading of American journalist James Foley by Islamic State militants "shocked the conscience of the entire world" and he vowed the United States would do what it must to protect its citizens.
US officials, meanwhile, said American warplanes continued to strike IS targets in Iraq.
Islamic State posted a video yesterday that purported to show the beheading of Foley in revenge for US air strikes in Iraq. It prompted widespread revulsion that could push Western powers into further action against the group.
US officials said that intelligence analysts had concluded that the video, titled "A Message to America," was authentic. It also showed images of another US journalist, Steven Sotloff, whose fate Islamic State said depends on how the United States acts in Iraq.
The gruesome video presented Obama with bleak options that could define American involvement in Iraq and the public reaction to it, potentially dragging him further into a conflict he built much of his presidency on ending.
"Jim was taken from us in an act of violence that shocked the conscience of the entire world," Obama said in brief comments to reporters in Edgartown, Massachusetts, where he has been vacationing. He said he had spoken with Foley's family.
"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," Obama said. "When people harm Americans, anywhere, we do what's necessary to see that justice is done."
British anti-terrorist police began an investigation of the video, in which Foley's killer spoke with a London accent.
Apparently a British national, the killer is just one of hundreds of European Muslims drawn to join Islamic State in Iraq and Syria and who authorities say pose a security threat to US and European interests if they return home from the Middle East.
The video showed a high level of technical proficiency and the use of a British voice may have been intended to make its contents clear to audiences in the United States, Islamic State's declared enemy.
Political leaders were swift to react.
British Prime Minister David Cameron interrupted his holiday to return to London to lead the hunt to identify the killer.
Foreign Secretary Philip Hammond said he was not surprised to hear the British accent and that large numbers of British nationals were fighting in Iraq and Syria.