Naturalised Irish citizens who travel to take part in conflict should have their citizenship revoked, the chairman of an Irish Muslim group has said.
Dr Umar Al Qadri was speaking after an Irish passport holder was captured in Syria by Kurdish-led forces fighting so-called Islamic State.
The man, who is in his mid-40s, is originally from Belarus.
He came to Ireland in 2000 and lived and worked in south Dublin for a number of years.
The man was known to gardaí (Irish police) as an Islamic State sympathiser before he left Ireland with his wife and family in 2013 to travel to the Middle East.
Dr Qadri is the chairperson of the Irish Muslim Peace and Integration Council.
He 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.
Dr Qadri described them as dangerous people who remain so even in prison because they may radicalise others.
He also criticised Taoiseach (Prime Minister) Leo Varadkar's comment that consular assistance would be available to any such person abroad.
Dr Qadri said Ireland needed to send out a strong message to people who have chosen to leave the state and fight abroad that the country is against extremism.
Speaking in Mali earlier, Mr Varadkar said: "The information we have is that an Irish citizen has been taken into custody in Syria.
"We don't know the details of that so I can't comment on it in any detail, but what I can say is that any Irish citizen around the world is entitled to consular assistance and will get that."
A spokesperson for the Department of Foreign Affairs said no requests for consular assistance on behalf of an Irish citizen captured in Syria have been made to it.