A 21-year-old man remains on a life-support machine at the intensive care unit in Kerry General Hospital, Tralee, after being assaulted near the town centre on Thursday evening.
Gardaí are appealing for information about the attack at Brewery Road, a busy spot close to houses, sports and community facilities just north of the town centre, between 6.15pm and 6.30pm.
The assault left the victim with serious head injuries and was unprovoked, gardaí believe.
It appears the victim, who is from Tralee and employed locally, had left a house nearby and was walking alone at the time of the attack.
A passerby discovered the young man lying on the street at the scene.
It was suspected first that he was kicked in the head several times. Emergency services were called and he was removed by ambulance to Kerry General.
His condition last night was described as stable but critical. The scene of the attack is directly opposite the popular Tralee greyhound track.
The area was cordoned off for much of yesterday and was being forensically examined.
Gardaí issued an appeal for witnesses to the attack and for anyone who saw anything suspicious at the time.
Supt Pat Sullivan, Tralee, said: "This was a vicious assault carried out in broad daylight in a busy part of Tralee."
Traffic would have been passing at the time and there are a lot of houses in the area, he said.
Both the attacker and the victim were on their own at the time, according to information gathered so far by gardaí.
Supt Sullivan said it was not known if an implement was used in the attack. Detailed searches were being carried out in the area, including a search of a graveyard.
Anyone with information should contact the Garda in Tralee by calling 066-22022, or any Garda station, Supt Sullivan said.
A description of a man in his mid-30s seen leaving the area on foot was issued by gardaí last night.
The man is about 185cm (6ft 1in) and of stocky build. He had a tight haircut and was wearing dark pants or jeans and a navy blue windbreaker-type anorak with stripes on the elbows.
Gardaí wish to speak to anyone who was in the area of St Brendan's church car park at the time.
Tralee town councillor Kieran Moriarty (FF) said he feared the town was in danger of getting a reputation as a "second stab city" because of the constant reports of crime.
He said while Tralee was no better or worse than any other town or city in relation to crime, reports in the national media of violent incidents could influence inward investment.
Most assaults in Tralee occur in the early hours.
Recently it emerged that a reduction in late-night opening hours by half an hour had led to a dramatic reduction in public order offences and assaults on gardaí.
However general assaults and assaults causing harm have not been reduced, Supt Sullivan told a recent meeting of the town's joint policing committee.
In fact, section three assaults (assault causing harm under the Non-fatal Offences Against the Person Act) continued, and some of these within pubs and nightclubs were being deliberately disguised by proprietors, Sup Sullivan told the meeting in Tralee a week ago.