Speaking with a London accent, the man, a member of the so-called Islamic State of Iraq and the Levant (ISIL), says the "doors of jihad are still open", encouraging people to fight in the war against the Syrian government, the Telegraph reported Saturday.

Dressed in camouflage and wearing a balaclava, he addresses his British "brothers" telling them to join the growing ranks of foreign militants.

He claims to have already managed to help others make the journey to Syria. Most travel to the porous border with Turkey where they go through with relatively few checks from authorities.

Sitting on top of an anti-aircraft gun, the masked man speaking from Hama, in the west of Syria, tells the camera: "Put your trust in him (God) and he will guide you to these lands."

Another man speaking in English with a British accent then seemed to respond to police warnings that travel to Syria could result in jail terms, saying, “Greetings from the blessed lands of Sham [Syria]; the lands that the kuffar [unbelievers] back home tell you that if you try to reach here there will be consequence for you."

Another British extremist militant with ISIL - dubbed too extreme even for Al-Qaeda after they publicly distanced themselves from the group - tweeted a picture of a poster reading “Keep Calm, Support ISIL”, parodying the Second World War motivational slogan.

Western governments and intelligence agencies have expressed their concerns that the steady stream of extremists leaving their countries to fight in Syria are both fueling the conflict there and pose a potential security threat should they return home someday.

Up to 400 Britons are thought to currently be fighting in Syria and at least eight are known to have died.

Syria has been gripped by deadly unrest since 2011. According to reports, Western powers and their regional allies - especially Qatar, Saudi Arabia, and Turkey - are supporting the militants operating inside the country.

NTJ/SHI