The main suspect in the latest propaganda video by so-called Islamic State is thought to be British man Siddhartha Dhar, the BBC understands.

An official source told the BBC Mr Dhar was the focus of investigations into the video, which purports to show the killing of five men IS says were spies.

Mr Dhar, also known as Abu Rumaysah, fled Britain in 2014 while on bail.

In August 2014 Siddhartha Dhar participated in a BBC debate, hosted by Asian Network reporter Catrin Nye, with young British Muslims about living in a Caliphate.