A total of 30 Irish people have gone to fight there as of November 2015, according to The Soufan Group (TSG).
This is effectively unchanged since a 2014 report by TSG, which put the number of Irish foreign fighters at between 25-30.
Ireland’s figures buck the trend for most of Western Europe, where numbers of foreign fighters have doubled in the last year.
This is driven by surges in the main countries — France, Germany, Britain and Belgium — which between them account for 3,700 of the 5,000-plus fighters from Western Europe.
The figures come at a time when an outspoken Sunni cleric in Dublin again urged both the Government and sections of the Muslim community to take specific actions to combat radicalisation.
Shaykh Umar Al-Qadri, of the Al-Mustafa Islamic Centre in Blanchardstown, Dublin, said the necessary collaboration between the State and the Muslim community was “not happening”.
The latest report from TSG, entitled Foreign Fighters, said the numbers from Western Europe have “more than doubled” since their previous study in June 2014.
The New-York based security intelligence organisation said the average rate of returnees to Western countries was now around 20%-30%.
This would indicate that between six and nine Irish people, out of the 30 who have gone, have come back home.
The TSG report said returned fighters presented “a significant threat to security and law enforcement agencies that must assess the threat they pose”.
It said that, while the number returning was increasing, their motivation for so doing varied.
It said some had enough of violence, others had become disillusioned with IS and others again wanted to pursue their goals elsewhere.
The report said the appeal of Islamic State “appeared to be as strong as before despite — or in some cases because of — the multiplying examples of its horrific violence and increasing totalitarianism”.
It said the motivation of young people to travel to Syria was “more personal than political” and much of the IS video productions appealed to people who “seek a new beginning rather than revenge past acts”.
The report estimates that 1,700 people have travelled from France (up from 700 in June 2014). In addition, 760 have gone from Britain (400), 760 from Germany (270) and 470 from Belgium (250).
Speaking on the Marian Finucane Show on RTÉ, Dr Al-Qadri said there was a responsibility on the Government to hold workshops in mosques and schools to make young Irish Muslims “immune from radicalisation”.
He said: “We need projects to promote integration. Unfortunately, we don’t see that happening. We don’t see collaboration between the Government and Muslim organisations.”
He again criticised some leading Muslim organisations for “turning a blind eye to radicalisation”.