In comments alongside a video released by the so-called Islamic State of Iraq and the Levant (ISIL), extremists claim that the man, who calls himself Abu Issa al-Andalusi, grew up in Portugal before playing for the north London club.

In the video, al-Andalusi appears wearing a face mask and urges others to join the war.

Al-Qaeda breakaway group ISIL has been blamed for the massacre of civilians, and is locked in a struggle with other militants and the Syrian army for the control of swathes of northern Syria.

The posting reads: "He grew up with Ronaldo, played for Arsenal, and [then] left football, money and the European way of life for the sake of Allah."

The two videos have been released on extremist site FiSyria.com, and are addressed to recruit from Russian-speaking countries.

One has now been removed by video hosting site YouTube for contravening hate speech policies.

The man, who speaks English with a heavy Portuguese accent, appears by a lake and boasts and claims that ISIL has "conquered many cities" and is "implementing sharia".

He says: "If you have family in these [western] countries what is going to happen probably. You don't have control over your children. Maybe in some of countries it's a must for you to put your children in the kaffir schools."

The Middle East Research Institute said that the site has been active for two years, and provides propaganda on the activities of ISIL to Russian speakers.

"At least some of the people behind the site are in Syria themselves," said a spokesman.

"The site regularly brings videos from the field showing video messages and talks of militants, news reports, scenes and footage of combat, and general extremist material."

An Arsenal spokesman said: "We do not recognize the individual from the published clips and we don't have any record of an Abu Isa al-Andalusi representing the club at any level."

NTJ/HH