AFP — British Prime Minister David Cameron said that Britain would refuse to be cowed by Islamic State terrorists, while Foreign Minister Philip Hammond said that British airstrikes were not being ruled out.

IS warned a British hostage would be next unless London backs off from its support for Washington’s air campaign.

It also said the journalist’s killing, which comes on the heels of the beheading last month of another US reporter, James Foley, was in retaliation for expanded US airstrikes against its fighters in Iraq over the past week.

The masked executioner in the video spoke with a London accent and claimed to be the same man, confirmed by UK security services as a Briton, who beheaded Foley.The British prime minister said the beheading video depicted an “absolutely disgusting, despicable act” and chaired a meeting of security chiefs to discuss how to tackle the IS threat.

“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.

“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.

At the end of the five-minute recording, the militant threatens another captive, identified as Briton David Cawthorne Haines.

“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,” he says.

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.

“I can assure you that we will look at every possible option to protect this person,” the British foreign minister said.

“We have to deal with (IS) on the basis of the wider threat that they pose to the British public as well as this individual,” Hammond added.

“If we judge that airstrikes could be beneficial, could be the best way to do that, then we will certainly consider them but we have made no decision to do so at the moment.”

Britain has not so far carried out any strikes of its own against jihadist targets in Iraq but it has made extensive reconnaissance flights in support of the US air campaign from its base in Cyprus.

‘Brave and talented’

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.”

Israeli media reported that the family was Jewish and that Sotloff himself held joint US-Israeli nationality but IS made no mention of either in its video.

Sotloff’s former employers at Time and Foreign Policy paid tribute to a man widely respected for his intrepid reporting in Syria and the wider region, including a previous stint in Libya.

UN Secretary General Ban Ki-moon said the world was outraged at the apparent beheading.

Hours after the posting of the video, the White House announced that Obama had authorized about 350 more US troops to beef up security at US diplomatic facilities and protect personnel in Baghdad.