A British man who fought alongside al-Qaida-linked extremists in Syria funded his militant ambitions by mugging people on the streets of London.

Choukri Ellekhlifi, 22, threatened wealthy residents of London's exclusive Belgravia neighbourhood with a high-voltage stun gun and forced them to hand over their valuables, claims the Daily Mail.

Ellekhlifi, who died in an attack by pro-Assad forces near the city of Aleppo in August, was part of a group of 10 British jihadists who joined 20 other Britons to fight alongside Syrian opposition group Jabhat al-Nusra, which is linked to al-Qaida.

Months before his death, Ellekhlifi was found guilty by Woolwich Crown Court of carrying out eight late-night robberies with accomplices Mohamed Elyasse Taleouine, 21 and Mohamed Ibrahim, 23. Ellekhlifi was released on bail and subsequently fled to join rebels in Syria.

Police launched an investigation into the robberies in August and searched the homes of Ellekhlifi, Ibrahim and Taleouine, where they found stolen property.

"Wearing masks, they would approach their victims on bicycles, threaten them with a stun gun and demand they hand over their possessions," a security source told the Daily Mail.

Two of the trio's victims were hospitalised with head injuries after they were shot with a Taser-style gun.

Ellekhlifi, who was of Moroccan descent, used the pseudonym Abu Hujama al-Britani. A picture of a fighter in Syria using the Abu Hujama alias recently surfaced on the internet but Abu Hujama has now been identified as Ellekhlifi, who lived in Paddington, west London.

Estimates suggest that up to 300 young British people have travelled to join the civil war in Syria.