BAGHDAD- Islamic State jihadists have beheaded a second American reporter, releasing video of what it said was retaliation for expanded US air strikes in Iraq, hours before President Barack Obama ordered more troops to Baghdad.
Washington confirmed that the video of the execution of 31-year-old reporter Steven Sotloff, which a US spokeswoman described as "sickening", was authentic.
As Iraqi forces kept up their fightback against the jihadists northeast of Baghdad, IS warned that a British hostage would be next unless London backed off from support for Washington's air campaign in Iraq.
The masked executioner in the video spoke with a London accent, and claimed to be the same man, dubbed Jihadi John by the British press, who beheaded US journalist James Foley, 40, in a similar posting last month.
In the latest footage, Sotloff calmly addresses the camera to say he is a victim of Obama's decision to press on with air strikes against the jihadists in Iraq.
At the end of the five-minute video recording, discovered online by the SITE Intelligence monitoring group and seen by AFP, the militant threatens another captive, identified as Briton David Cawthorne Haines.
"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State," the black-clad jihadist says, wielding a combat knife.
The militant condemns US air strikes against IS fighters around both Mosul Dam in the north and the Shiite Turkmen town of Amerli further south, which dates the video to the past week.
"So just as your missiles continue to strike the necks of our people, our knife will continue to strike the necks of your people," he declares, before reaching round to cut his captive's throat.
In a warning to Britain, the killer declares: "We take this opportunity to warn those governments that enter this evil alliance of America against the Islamic State to back off and leave our people alone."
Britain has maintained a media silence about the kidnapping of aid worker Cawthorne Haines and there were few immediate details about when or how he was abducted.
In a statement, the Sotloff family, who live in Miami, said: "The family knows of this horrific tragedy and is grieving privately. There will be no public comment from the family during this difficult time."
After Foley's death, Sotloff's mother Shirley had addressed a video message to IS leader Abu Bakr al-Baghdadi pleading for her son's life, and insisting he had no influence on US policy.
British Prime Minister David Cameron said the video depicted an "absolutely disgusting, despicable act" and convened a meeting of security chiefs to discuss how to tackle the IS threat.
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