A man is still being questioned in Dublin as part of an investigation into dissident and criminal activity.
He was arrested yesterday, becoming the fourth man to be held this week.
The 54-year-old man is being held under Section 4 of the Criminal Justice Act at Store Street Garda Station.
He was detained in the north inner city on Thursday.
The three other men appeared before the Criminal Courts of Justice yesterday and were remanded on bail, with very strict conditions.
Separately, a fifth man, who was this week questioned over threats he is believed to have made against US President Barack Obama, was also released yesterday, this time without charge.
A file on that case will be sent to the Director of Public Prosecutions.