The New York Times, in an article about the Turkey airport terror attack, said the presence of large numbers of Russian-speaking fighters in Syria has been widely reported.
It cited the account of a French citizen Reda Hame, who was arrested in Paris last August soon after returning from Syria.
Hame allegedly told interrogators with France's domestic intelligence wing that he had been recruited by the external operations arm of ISIS and "assigned to create mayhem at a rock concert in France," the report said.
It said since 2014, the Islamic State has been trying to mount attacks in the West through a unit described in intelligence documents as the group's external operations branch, headed by the militant group's spokesman, Abu Muhammad al-Adnani.
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In the past two years, this branch has sent at least 20 operatives, trained in Syria and mostly French speakers, to Europe and Lebanon, possibly because they could fit in more and assume a more Western appearance, analysts said.
According to the International Crisis Group, up to 4,000 volunteers from Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan had joined the militant group by the end of 2015.
In Central Asian states like Uzbekistan and Kyrgyzstan, the recruitment of fighters for the Islamic State has been spurred by government repression against Muslim organisations as well as widespread poverty.
Last month, US-based private SITE Intelligence Group had said that ISIS had launched a new propaganda video that showed off a large group of Kalashnikov-wielding jihadists allegedly from India fighting against the Syrian forces in the Homs province.