Up to six Islamist terrorist groups had units in the Republic three years ago to deliver financial and logistic support to other cells abroad, according to declassified official US papers.
The documents, detailing contacts between the US embassy in Dublin and Washington-based agencies, were released to RTÉ under the US Freedom of Information Act.
Asked if any "foreign terrorist groups" had a presence in Ireland, the embassy named the Egyptian Islamic Jihad, Al-Gama'at al-Islamiyah, the Algerian Armed Islamic Group, al-Qaeda, and "possibly Hamas and the Palestinian Islamic Jihad".
Asked to describe the presence, the embassy said there are "operational support, logistical and financial cells located in Ireland". Asked if there are "any ethnic or religious communities in the country that are sympathetic to these groups", the embassy said yes. Asked if there had been any anti-American demonstrations in Ireland over the previous 12 months, the embassy said yes, and estimated the average size of a protest at between "30 to 300 people".
Meanwhile, the embassy also told the US state department that there were "suspect non-governmental organisations in the country that have a relationship" with some of the groups.
In another briefing document prepared for the 2002 visit by the then US health secretary Tommy Thompson, the then US ambassador, Richard Egan, said the Government had "offered crucial support" to the US in its role as president of the UN Security Council following September 11th.
"Moreover, despite strong public opposition to any US-led military action against Iraq - with or without UN Security Council authorisation - the Government of Ireland voted on November 8th, along with the other 14 UNSC members, to support the strong US/UK-sponsored resolution". The resolution passed on that date found Iraq to be "in material breach of its obligations" and vowed "serious consequences if Iraq did not fully and immediately disarm".
Fine Gael TD Billy Timmins said reports that Islamic terrorist cells were operating in Ireland three years ago were profoundly worrying.
"It is vital that the necessary funding be made available to our own intelligence services to counter threats such as these. I do not believe this has happened to date," said the Wicklow TD.