An Imam has called on gardaí to investigate religious groups that could be contributing to the radicalisation of members.
Shaykh Dr Umar Al-Qadri, chair of the Irish Muslim Peace & Integration Council, said "questions need to be asked" of religious groups that have a history of radicalised members.
His comments follow reports that two students studying medicine at NUI Galway died fighting for Isil in Syria and Iraq.
The two men, Mustapha al-Hayani and Tariq Mohainuteen, travelled from Galway to Dublin in September 2013 on the way to join Isil, the 'Sunday Times' reported.
Hayani was a graduate of the NUIG medical programme, while Mohainuteen was a visiting Malaysian student.
It is believed the men became radicalised while living in Galway.
Mohainuteen travelled to Turkey before moving into Syria, where he died during a battle against Al-Nusra.
Hayani, who flew directly to Iraq, was also killed in fighting, but the date and location of his death is unknown.
Shaykh Dr Umar Al-Qadri said gardaí need to look into what groups and communities the two men were involved with before they left.
"To what extent was their involvement? Were they official position holders? And if not, were they active members?
"These are some of the important questions that need to be investigated by gardaí," he told the Irish Independent.
"If somebody from my congregation had left for Isil, I would then be really worried and concerned that somebody really active in my community and congregation has left.
"It basically means I have failed in my duty and that someone who was very vulnerable and in my community has been radicalised, and that's my failure as [a matter of] leadership."