London: The terrorist dubbed "new Jihadi John" and appeared in the latest Islamic State video threatening attacks on the UK is believed to be Indian-origin British Muslim convert, media reports said on Tuesday.
Siddhartha Dhar, also known as Abu Rumaysah, had skipped bail and fled Britain in 2014 with his wife and their four children to join Islamic State in Syria.
Born a Hindu, the 32-year-old ran a business renting out bouncy castles in London before converting to Islam and joining the radical Islamist group Al Muhajiroun.
An official source told the BBC that Dhar is the focus of investigations into the video, which purports to show the killing of five men Islamic State says were spying for the UK.
Dhar's mother and sister have also watched the video, released by Islamic State on Sunday, and noticed 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," his mother Sobita Dhar told The Daily Telegraph.
His sister, Konika Dhar, from north London, said: "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 said her brother had converted to Islam more than 10 years ago and her memories of him are from when they were children and teenagers.
"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," she added.
One of Dhar's former business associates told the BBC he had "no doubt" the voice on the video was that of Dhar, who had been arrested on suspicion of encouraging terrorism by the British police but was later able to travel to Syria after being bailed.
His 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.
In one interview around that time he said: "We believe that whenever the sharia is established, the pure Islamic state maybe in Iraq or Syria, one day the leader will wage jihad and annexe Britain into the Islamic state.
"We are not going to forget Europe, we are not going to forget Britain, the armies will be sent here to conquer these lands."
In the latest ISIS video, he is now believed to be the masked man speaking in a British accent and holding a gun. He says: "We will continue to wage jihad, break borders and one day invade your land where we will rule by the Sharia."
British Prime Minister David Cameron on Monday said the video was "desperate stuff" from a group that was "losing territory".
The 11-minute video also features a little boy speaking in a British accent.
Channel 4 News has reported that a south London man named Sunday Dare recognised the boy in the video as his grandson, Isa Dare, who was taken to Syria by his daughter Grace Dare aka Khadija.
In the video, five men, wearing jumpsuits and kneeling in a desert location, appear to be shot in the back of the head, after making what is claimed to be their confessions.