Another US journalist has been beheaded at the hands of an apparently British jihadist on behalf of the Islamic State (ISIS) in Iraq, who also threatened to kill a British man.

Freelance journalist Steven Sotloff's murder was videoed and broadcast yesterday with a series of threats and statements from the militant group. Again, the victim was kneeling in an orange suit, with the apparently British jihadist wielding a knife above his head before the beheading. The voice of the jihadist was similar to that in the video of US journalist James Foley's murder. Foreign Secretary Philip Hammond told the BBC that the video appears authentic.

Steven Sotloff was a freelance journalist who had worked for Time magazine among others. He entered Syria last year to report on the suffering of Syrian people in refugee camps but was captured shortly afterwards.

Sotloff's mother, Shirley, had previously made a video asking for mercy for her son. The family say they intend to grieve in private. US President Barack Obama said justice for this "horrific act of violence" would be served against the murderers. "We cannot begin to imagine the agony everyone who loves Steven is feeling right now," he said. "Our country grieves with them".

In the video, the militant also threatened to kill a British hostage, though the hostage's name has not been released at the request of the victim's family. The Government is convening an emergency Cobra meeting today to address the situation.

The UK has so far not joined in with US air strikes in the region against ISIS, but there have been calls for British involvement in military action, including from former Foreign Secretary Jack Straw. US media reports suggest that the new killing will increase pressure on Obama to launch airstrikes in Syria as well as Iraq. Other options are attempted rescue missions on the ground, though Foreign Secretary Philip Hammond said that one had already been attempted and had failed. 

The jihadist in the video made a series of political statements, warning Obama to 'back off' from ISIS and said the killings were due to the foreign policy of the US.

This could be a reference to the US support for militias who have just successfully fought off ISIS in the town of Amerli, Iraq, following a three month siege. 

However another reason for targeting the American and British hostages may be that the jihadists' demands for cash were ignored. There have been a number of Western hostages held by ISIS, including aid workers. Other European hostages have reportedly been released after their governments paid ransoms. 

This ransom money is a significant source of income for the extremists. The Archbishop of York John Sentamu, told Good Morning Britain that ransoms should never be paid.

"Britain and United states are right never to pay ransoms because people abduct people and take them in order to get more money... it's a form of slave trade really," he said. "Everybody knows that blackmailers, if you give them one thing, they'll come back again and again and again." He also called on the United Nations to act in the situation.

Terrorism expert Rita Katz, from the Site Intelligence Group that found the beheading video before it was released by the jihadists, has warned that the videos are being used to intimidate the West, and also to recruit Western Muslims to the jihadist cause. "Prospective jihadists from the West, as is well-illustrated on social media, are now watching this video and seeing life under IS as something they could be a part of - a community comprised of people with the same backgrounds as them who heroically fight the enemies of Islam," she said in a blog post. 

Some British Muslims, including those from the liberal-leaning Muslim think-tank Quillium, have launched a fatwa against ISIS.