Armed detectives investigating the activities of the so-called New IRA made two "highly significant" arrests and seized €10,000 in cash as part of a major surveillance operation.
Details of Friday night's dramatic arrest operation have not emerged until now. One of the arrested men is a well-known dissident republican who is based in the Ballymun area.
He was arrested with a Belfast man who has been a top target for the PSNI, according to sources.
The 53-year-old Ballymun resident, who is originally from Finglas, is already facing charges of membership of an unlawful organisation after a major garda investigation last year in Dublin.
The Special Detective Unit (SDU) pounced on the suspects in a hotel near Dundalk, Co Louth, on Friday where it is believed a "cash handover" was taking place.
It is suspected that the Belfast man was meeting the Dublin dissident to collect cash to bring back over the border.
However, heavily armed officers were watching and they pounced on the suspects, who were arrested before being released without charge over the weekend.
It is understood that the pair were questioned about being members of the IRA.
The Dublin suspect was previously close to a north Dublin IRA figure who had close links to slain drug dealer Martin 'Marlo' Hyland who was shot dead in Finglas in December, 2006.
The 'business' relationship between Hyland and the IRA figures was the subject of a major Revenue investigation in the years before 'Marlo' was murdered by his own gang.
However, unlike his mentor who was involved in the Provisional IRA, it is now suspected that the Dublin dissident is involved with the so-called New IRA.
The New IRA is currently considered the biggest threat among the many different dissident republican factions.
The group is an amalgamation of the Real IRA, Republican Action Against Drugs and other republicans who came together to form one group in 2012.Sources say that its power base has "slowly continued to grow".
In one of the most serious developments, the New IRA claimed responsibility for the van bomb attack which led to the murder of prison officer Adrian Ismay last month.
The father-of-three suffered serious leg injuries when a car bomb exploded underneath his van on March 4.
He had surgery and subsequently returned home but was rushed to hospital again 11 days later before he died.