IS killer 'Jihadi John II' may be UK citizen Siddhartha Dhar

British Muslim convert Siddhartha Dhar, 32, a former bouncy castle salesman from London, may be the killer on the latest Islamic State video, says his family.

Scotland Yard on Tuesday said it was following developments on the footage showing a man with a British accent ranting against PM David Cameron before he and others shoot dead five hostages.

The video revived memories of 'Jihadi John', another British IS member who appeared in videos in which hostages were murdered.

Dhar's mother and sister said they noticed similarities in the voice of the man on the latest tape and Dhar. His sister, Konika, said, "This is just so shocking for me."

Dhar, a Hindu, converted on marrying Aisha, a Muslim woman, and was radicalised. Now known as Abu Rumasayah, he was arrested in 2014 and was on bail before going to Syria with Aisha.