Know more about Siddhartha Dhar - new “Jihadi John” in ISIS

Siddhartha Dhar, who is also known as Abu Rumaysah, is a convert from Hinduism and a high-profile Islamist.

Pic courtesy: YouTube

London: British Prime Minister David Cameron on Monday condemned a new execution video by Islamic State (IS), calling it a "desperate stuff" from an organisation that is "losing anybody`s sympathy".

In the video released on Sunday, a masked IS executioner with British accent threatened to invade the UK and called British Prime Minister David Cameron an "imbecile", before executing five men who appeared shackled and dressed in orange boiler suits. They were accused of spying against the IS for the UK.

The footage revived memories of "Jihadi John", a British Islamic State member who appeared in several videos in which hostages were killed before his own death was reported in an air strike late last year.

Some British media speculated that the militant in the new video might be Siddhartha Dhar, who is also known as Abu Rumaysah, a convert from Hinduism and a high-profile Islamist, although security experts were divided on whether it was him.

The British-Indian Muslim convert left Britain with his family to travel to Syria despite being on police bail after being arrested in late 2014 on suspicion of being a member of a banned organisation.

Dhar's mentor is radical London cleric Anjem Choudary.

The United States said in November it had killed Mohammed Emwazi, who as "Jihadi John" had become a symbol of Islamic State. The voice and appearance of the masked militant shown in the new video was different from Emwazi, but he spoke in a clear English accent, waving a gun at the camera while criticising Cameron.

"This is a message to David Cameron, O slave of the White House, O mule of the Jews," the man said in the 10-minute video released on Sunday.

One would have thought you'd have learned the lessons of your pathetic master in Washington and his failed campaign against the Islamic State," the man said.

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.

Dhar's mother and sister have also watched the video, released by ISIS 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.

In November, British officials said that up to 800 Britons had travelled to Iraq and Syria, some to join Islamic State. About 50 percent had returned home while about 70 were believed to have been killed.

(With Agency inputs)