Gerry “The Monk” Hutch has been arrested by Spanish police as part of an international investigation into money laundering.
Mr Hutch, 61, was arrested along with other relatives in Spain and is being questioned by authorities.
It comes a day after a number of searches were carried out in the Republic of Ireland and Spain as part of an investigation into transnational organised crime.
Irish police said a crime gang is suspected to be involved in money laundering across a number of jurisdictions.
Ten searches were conducted in Spain on Wednesday morning while gardai from the Garda National Bureau of Criminal Investigation (GNBCI) are in Spain supporting the Guardia Civil.
An officer from the Guardia Civil attended the search of a residential property in Dublin on Wednesday, following a request by the Spanish authorities.
Irish police chief Drew Harris said the searches and arrest follow the sharing of information and evidence between Irish and Spanish police.
Speaking at the garda (Irish police) headquarters in Dublin, Mr Harris said: “There’s a judicial process ongoing with the Spanish authorities, so I cannot comment then on the specifics of yesterday’s operations and what’s going to unfold over the next couple of days.
“But I can say we’ve been engaged with Guardia Civil over a number of years, over two years, closely in terms of sharing information and then sharing evidence.
“We will see today and over the coming days, just what the immediate outturns are of that investigation.
“It’s another organised crime group. They’re a very well known one, and so there is an element of notoriety in respect of them.
“But beyond that then, is the extent of the criminality that they are engaged in.
“We’ve been involved in a long term and very thorough, focused investigation in respect of that organised crime group, and that has meant that we’ve worked with our international partners in trying to bring to an end the criminality that the overall organised crime groups involved in.
“It is significant in terms of our cooperation with the Spanish authorities in this case and Europol. As the next couple of days unfold, will see some of the out turn of that.”
Minister for Justice Helen McEntee said: “I am not going to comment on any case, but what I will say that is that it is very clear, by a number of actions recently, that An Garda Siochana are working very closely with our European and international counterparts, to bring those involved in organised crime to justice.
“We know crime knows no boundaries, we know that people, to evade the law, will often leave the country and cross over to other jurisdictions and that’s why it is really important that gardai have built up really strong relationships with other police in other countries.
“I travelled to the UAE this week to sign a number of treaties to make sure that corporation can be strengthened, and above all those responsible for inflicting nothing but misery in our communities, the length and breadth of this country, that the people at the very top are held accountable.”
