The chairperson of the Irish Muslim Peace and Integration Council has said naturalised Irish citizens who travel abroad to take part in conflict should have their citizenship revoked.
Dr Umar Al Qadri was speaking following reports from Syria that an Irish passport holder has been captured by Kurdish-led forces fighting the Islamic State militant group.
He came to Ireland in 2000 and lived and worked in south Dublin for a number of years.
Gardaí have said he was not known to them when he was granted citizenship, but was subsequently radicalised by an individual whom they say also radicalised a number of other people in Ireland.
Dr Qadri has said that naturalised Irish citizens who leave to fight abroad should be not be accepted back in Ireland, but deported to their countries of origin.
He described them as dangerous people who remain so in jail, because they may radicalise others.
He also criticised Taoiseach Leo Varadkar's comment that consular assistance would be available to any such person abroad.
Dr Qadri insisted that Ireland needs to send out a strong message to people who have chosen to leave the State and fight abroad that the country is against extremism.
There is precedence for deporting people who are considered a threat to the State and the courts have upheld the right of the State to do so.
One such person whom gardaí say posed a serious threat to the security of the State and radicalised a number of people while here has already been deported.
A second case is being challenged and is currently before the Supreme Court.
The Department of Justice has said it is policy not to comment on security matters or indeed on individual cases.
However, officials are liaising with gardaí and the minister is monitoring the situation, a spokesperson said.
They said: "In regard to the EU directive on combating terrorism, the main provisions of it already exist in Irish law and it is the intention for Ireland to opt in.
"Irish citizenship, including citizenship through naturalisation, is governed by the Irish Nationality and Citizenship Act 1956 as amended. Under this Act, in proscribed circumstances, citizenship may be revoked.
"In line with this legislation a committee has been established to examine individual cases and make recommendations to the Minister for Justice."