An Australian jihadist in an ISIS propaganda video. Screenshot/http://www.abc.net.au/news/2014-06-20/isis-fighter-identfied-as-an-australian-in-recruitment-video/5540116 Australia has become the largest per capita contributor of foreign fighters to the extremist group the Islamic State of Iraq and the Levant (ISIS), a jihadist organization that controls much of Syria and Iraq, ABC News reports.

An estimated 150 to 300 Australian citizens and residents have left the country to join radical militant groups in the Middle East. A majority of those volunteers have gone on to join ISIS, where they are playing key roles in helping to increase further recruitment of foreign fighters.

"The Government is gravely concerned by the fact that Australian citizens are heading to Iraq and Syria not only to fight but to take leadership roles in radicalizing others in these conflicts," Australian Foreign Affairs Minister Julie Bishop said on the television show Question Time.

Two Australians recently released a 13-minute long video titled "There Is No Life Without Jihad." In the video, the Australians urged, in English, for potential jihadists from America to Australia to come to the Middle East and help ISIS establish an Islamic Caliphate.

ISIS is estimated of having upwards of 11,000 fighters spread between Iraq and Syria. Around 3,000 of them are thought to be foreign fighters, with an estimated 500 coming from western Europe.

Australia has so far reacted to its citizens' alleged jihadist roles in Iraq and Syria by canceling passports in an attempt to ensure that suspected jihadists would be unable to return home and carry out attacks. At least fifty passports have been declared void so far.