Detectives are investigating reports that INLA thugs Declan 'Whacker' Duffy and Dessie 'Border Fox' O'Hare were among a group of men involved in two separate serious incidents.
Gardai in Rathcoole are probing the incidents, which occurred just 15 minutes apart at an estate in the Citywest area.
A Kildare-based businessman aged in his 40s was kidnapped at 11.45am on Tuesday. He was brought to a house where he was assaulted.
His injuries were not serious enough to require hospital treatment and he refused to make a complaint to gardai about his ordeal.
Then, at noon, a 40-year-old security guard was brought from the same house, where the initial assault happened, to a location called Garter Lane in Saggart and suffered injuries much worse than in the earlier assault.
The seriously injured man, who is from Clondalkin, was rushed to Tallaght Hospital. He is believed to have suffered a fractured skull and a broken nose and jaw. His two arms were also broken and he suffered cuts and bruises to his legs. It's understood he told gardai that he sustained the injuries after falling and also refused to make a complaint.
"This fella was beaten to a pulp, the older man did not suffer anything like the same injuries," a source explained.
Gardai believe the assaults are linked to INLA extortion activities in the capital and are trying to establish which dissident figures were involved in the savage attacks.
However, sources say that "reliable information" has come in that both Duffy and O'Hare were present along with a feared Tallaght criminal.
In April, the Herald revealed that gardai were looking to speak to Duffy after a Mercedes car owned by a 68-year-old businessman was burnt out by associates of the gangland thug in the Glasnevin area of the capital.
Originally from Armagh, Duffy is now spending a lot of time in Dublin's south inner city. He joined the INLA in the 1980s and was still a teenager when he was involved in the murder of Sergeant Michael Newman in Derby, England in 1992.
It was not until July 2010 that he was convicted and received a life sentence for the murder of the unarmed police officer.
Like Duffy, O' Hare was also released under the Good Friday Agreement after being given a 40-year sentence for kidnapping and mutilating Dublin dentist John O'Grady in 1987 and was linked to multiple murders during the Troubles.