London, Sep 4 (IANS/EFE): British Prime Minister David Cameron chaired an emergency session of Cobra committee Wednesday to discuss the threat by Islamic State (IS) militants to follow up the beheading of two US journalists with the murder of a British hostage.

The committee of senior ministers will assess a British response to the threat to kill a British hostage after US journalists James Foley and Steven Sotloff were beheaded on camera, apparently by an IS militant who was educated in Britain, Efe quoted British officials as saying.

Cameron described the video of Sotloff's execution, entitled "a second message to the United States", as "despicable", adding that it was similar to one released by IS in late August, showing Foley's murder.

The IS had threatened to kill Sotloff if US President Barack Obama continued his country's campaign of targeting positions in Iraq under IS control.

The British government has confirmed that IS is holding a Briton as hostage, who has been identified in the international media as David Haines.

The media have also been reporting that the secret services are using voice identification technology to confirm the identity of the Briton who presumably killed the two journalists.