Two teenagers and a young man were arrested after a 22-year-old was beaten and repeatedly kicked in the head during a vicious assault in south Dublin.
The attack happened in the O'Rourke Park area of Sallynoggin over the weekend following a house party in which one man suffered horrific slash injuries.
The victim of the assault was left in a critical condition in hospital, where he remains, with sources saying he was kicked in the head several times after being knocked out.
Both the slashing and the assault happened within a short space of time in the same area and gardaí believe they are connected.
In the early hours of Sunday morning a man suffered horrific knife wounds to his face and arm after being attacked during a house party.
It's understood one of the wounds on his face stretched from his ear to his mouth.
The victim, in his late teens, was hospitalised.
A short time later, at around 2am, a 22-year-old man was set upon outside a house on O'Rourke Park.
Emergency services responded and found the young man unconscious on the road with serious injuries to his head.
He was rushed to St Vincent's Hospital in south Dublin, but has since been transferred to Beaumont Hospital, where he is in a critical condition.
Detectives believe that up to three males were involved in the attack.
In a follow-up search a 20-year-old man was arrested in the area and taken to Dún Laoghaire garda station for questioning.
He has since been released without charge.
Gardaí will now prepare a file for the DPP.
Investigators carried out further searches over the weekend and arrested two male teenagers on suspicion of involvement in the assault.
A garda spokesman said: "Both have since been released without charge and files will be prepared for the Garda Youth Diversion office."
A source told the Herald that both attacks had a high level of violence.
"The initial slash attack was very vicious and the injured male suffered one particularly nasty injury across the side of his face," the source said.
"Gardaí are still looking into what led to the attack but are satisfied it is a dispute among people from the area.
"They are also satisfied that an attack a short time later in O'Rourke Park is directly linked.
"This was a particularly vicious assault in which the injured man was attacked by at least three men," the source added.
"There was a high degree of violence used, and gardaí have since arrested three suspects as part of their investigation.
"All of those involved are local men, with the eldest suspect a person who has come to garda attention locally as well.
"A file has been submitted and the DPP will decide if charges will be brought down the line."
A garda spokesman added: "Gardaí in Dún Laoghaire are investigating two serious assaults that occurred at O'Rourke Park, Sallynoggin, Co Dublin, in the early hours of Sunday morning, August 16, at approximately 2am.
"Investigations are ongoing".