“The terrorist dubbed "new Jihadi John" and also appeared in the recent ISIS video, threatening attacks on the UK, is believed to be Indian-origin British Muslim convert,” the media reports said.

In 2014, Siddhartha Dhar, alias Abu Rumaysah, the 32 year old Hindu, had skipped bail and fled Britain, along with his wife and four children to join ISIS in Syria.

Dhar ran a business renting out bouncy castles in London, before converting to Islam and joining the radical Islamist group Al Muhajiroun.

Sources said that, Dhar is the focus of investigations into the video, which purports to show the killing of five men ISIS says were spying for the UK.

The ISIS video which was released on Sunday was watched by Dhar's mother and sister and noticed the similarities between the voice of the masked terrorist, being referred to as the ‘new Jihadi John’ by the British media.

"I heard the voice, yes, but I don't know, I'm not sure of the voice. These are the most difficult questions to answer. I just cannot say. I'm not sure within myself whether it is the truth or not," Dhar’s mother Sobita Dhar said.

Even Dhar sister Konika Dhar responded on the issue, saying, “I believed the audio to resemble, from what I remember, the voice of my brother but having viewed the short clip in detail, I wasn't entirely convinced which put me at ease. I can't believe it. This is just so shocking for me. I don't know what the authorities are doing to confirm the identity, but I need to know if it is.”

She further said that, 10 years ago, her brother had converted to Islam and she still recollects childhood memories of her, with her brother.   

She even added, “He was a very pleasant boy, and I know it may be hard to believe, but he still is, and I still believe that he still can be that person.”

Strengthening the voice to be Dhar’s, one of his former business associates said ‘no doubt’ the voice on the video was that of Dhar.

Dhar’s former neighbours from Walthamstow in east London claimed Dhar's wife was more devout than him and suggest she may have put him on the path to extremism.

In the months leading up to his arrest Dhar was accused of calling for the imposition of Sharia law in Britain.

By Phani Ch