A study of the social media activity of foreign jihadists showed many were following certain influential preachers -- one from the United States and another from Australia, said the International Centre for the Study of Radicalisation (ICSR) at King's College London university.
Their 36-page research paper entitled "Greenbirds: Measuring Importance and Influence in Syrian Foreign Fighter Networks" examines how foreign fighters in Syria receive information about the conflict and who inspires them.
Over the past 12 months, researchers studied the social media profiles of 190 Western fighters in Syria. More than two-thirds were affiliated with the jihadist Islamic State of Iraq and the Levant (ISIL) group or the Al-Qaeda affiliate Al-Nusra Front.
The research found that for the fighters they followed, social media has become an essential facet of the conflict.
"They are playing the role of cheerleaders"They found that a large number of foreign fighters received their information from "disseminators" -- unaffiliated but broadly sympathetic individuals mostly based in the West.
The ICSR said they had found "new spiritual authorities" who foreign fighters in Syria look to for inspiration and guidance.
"They are playing the role of cheerleaders," the report said.
"Their statements and interactions can be seen as providing encouragement, justification, and religious legitimacy for fighting in the Syrian conflict, and -- whether consciously or not -- play an important role in radicalising some individuals."
It stressed there was no evidence to suggest those individuals were involved in facilitating foreign fighters' entry into Syria or coordinating their activity with jihadist groups.
'Eloquent, charismatic' preachers
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Based on quantitative analysis of their popularity within foreign fighter networks, the paper identified the two most prominent of these new spiritual authorities as US-based Ahmad Musa Jibril and Musa Cerantonio, an Australian convert to Islam with Italian roots.
Jibril, who is in his early 40s, "does not explicitly call to violent jihad, but supports individual foreign fighters and justifies the Syrian conflict in highly emotive terms", the report said.
"He is eloquent, charismatic, and -- most importantly -- fluent in English."
Cerantonio, 29, has become an "outspoken cheerleader" for ISIL.
"Jibril is a subtle, careful, and nuanced preacher, while Musa Cerantonio is much more explicit in his support for the jihadist opposition in Syria," the paper said.
"Foreign fighters who follow them both are exposed to the same essential message: fighting in Syria is legitimate and honourable."
Nearly 55 percent were identified as members of ISIL, while just under 14 percent were through to belong to Al-Nusra.
Fighters that could not be clearly placed in one camp made up 29 percent.
The sample found 18 percent of the fighters came from Britain, followed by France (12 percent), Germany (11 percent), Sweden (10 percent), Belgium (nine percent) and the Netherlands (six percent).
In December 2013, the ICSR estimated that up to 11,000 people from 74 nations, including 2,800 from European or Western countries, had gone to Syria to fight.