An execution video recently released by ISIS appears to show a man with a British accent and young boy in military gear speaking in English, providing a stark reminder that Western-born militants are among the ranks of the Islamic State group.

U.K. Prime Minister David Cameron called the video "desperate stuff," adding the organization is losing ground in the region, but British officials have said up to 800 Britons have travelled to Iraq and Syria, while Canada puts its estimated number of people joining the conflict at 130. Many, but not all, are joining ISIS.

This is not the first time Western-born militants have appeared in ISIS media. Here are a few examples.

British PM condemns latest ISIS video2:06

Jihadi brides

Two Bosnian-born teenage girls went missing from Vienna, Austria, in April 2014. In a text message, one of the girls, 15-year-old Sabina Selimovic, told a French newspaper she and Samara Kesinovic, 17, ran off to Syria to marry Islamic State fighters and become so-called "jihadi brides."

The two, who came to Austria as refugees fleeing the Bosnian war, were labelled "poster girls for jihad" by the Austrian media. They were featured on ISIS social media channels wearing full burkas and brandishing AK-47 rifles. Austrian police said the images were meant to recruit young girls to ISIS.

In November 2015, Austrian media reported Kesinovic had been beaten to death after trying to escape Al-Raqqah, the Syrian city declared by ISIS as its de facto capital. Other reports said she was forced into sexual slavery before her death.

Her companion Selimovic was reportedly killed while fighting in Al-Raqqah. All reports have yet to be confirmed by the Austrian government.

Steven Emerson of the Washington, D.C.-based Investigative Project on Terrorism said ISIS has Western recruits appear in its media as a form of initiation, and that media featuring westerners appeals more to potential recruits in the West.

Canadians in ISIS

Andre Poulin, of Timmins, Ont., went to Syria in 2012 and joined ISIS.

After he was killed, reportedly fighting in an Aleppo airport, ISIS released a video featuring Poulin in an effort to recruit westerners.

In the video, which used scenes of Canadians playing hockey and gassing up snowmobiles, Poulin referred to Canada as "dar al-kufr," or land of disbelief.

Andrew Poulin's influence7:39

In 2014, Calgary's Farah Mohamed Shirdon was seen in an ISIS video burning his Canadian passport and issuing threats against the West.

It was believed Shirdon was killed in August, but Vice magazine used social media to track down and arrange a Skype interview with him in September, which led to the RCMP ordering Vice journalist Ben Makuch to hand over his correspondences with Shirdon.

Vice, a media company founded in Montreal, is fighting the RCMP's request in court.   

In December 2015, ISIS released a video featuring an Ottawa man calling on Muslims in Canada to carry out domestic lone-wolf attacks.

The man, identified by officials as John Maguire but referred to as Abu Anwar in the video, urged Canadians to follow in the footsteps of Parliament Hill shooter Michael Zehaf-Bibeau and Martin Couture-Rouleau, who ran down two officers with his car in Quebec, killing one of them.

Like Poulin, Maguire mentions playing hockey growing up, a calculated attempt some say to appeal to Canadians.

Canadian John Maguire appears in new ISIS video4:42

Jihadi John

In a series of gruesome ISIS videos showing either the killing or bodies of hostages, many noticed one of the masked, black-clad militants brandishing a knife spoke with a London-area accent, fuelling speculation the captor was a British national.

Former ISIS hostages referred to a trio of British-sounding captors as The Beatles, calling the man in the videos John, in reference to John Lennon.

Mohammed Emwazi

Mohammed Emwazi, known as Jihadi John, was raised in London and studied computer programming before joining ISIS in 2013. (University of Westminster/ISIS)

U.S. and British intelligence services used a variety of investigative techniques like voice and facial recognition technology to identify "Jihadi John" as Mohammed Emwazi, a Kuwaiti-born, London-raised computer programming graduate.

Emwazi, who came to the attention of the British security service MI5 in 2009 and left for Syria in 2013, became the target of allied drone attacks after he was identified and U.S. military is "reasonably certain" he was killed by an airstrike in 2015.