The second gang-type incident involved people wielding hurleys.
The innocent mugging victim was severely beaten.
Inspector Pat Lehane said the mugging was particularly unusual, because of the number of attackers and the severity of the assault.
The unprovoked attack took place when a 42-year-old man was walking home past the Flying Enterprise bar and restaurant, at the bottom of Barrack Street, between 10.45pm and 11pm last Monday.
“He was pulled into Cove Street by the men. He was kicked and punched repeatedly and suffered a number of blows to his head,” Inspector Lehane said.
He said gardaí believe up to five assailants were involved.
“It was an unusually vicious mugging,” the inspector said.
The injured man managed to make his way to Cork University Hospital.
The injuries to his head and jaw were described as being quite serious and medical experts were considering transferring him to a hospital in Dublin for further treatment.
“We are anxious to hear from anybody who was in the area at the time, from between 10.30pm and 11.30pm, and who may have seen a number of men acting suspiciously, or who may have seen the man being attacked,” Insp Lehane said.
Anybody with information is asked to contact Anglesea Street Garda Station at 021-452 2000.
Meanwhile, gardaí in Gurranabraher in the northside of the city are seeking witnesses to an attack on a man by a gang of youths, armed with hurleys.
The victim, who is 35 and lives locally, was walking along Harbour View Road in Knocknaheeny between 8.15pm and 8.40pm on Monday when he was attacked by the youths who struck him repeatedly with the hurleys.
He suffered a broken jaw, lost a number of teeth and had numerous lacerations to the head.
Superintendent Con Cadogan, heading the investigation, said the man was taken to the Mercy University Hospital for treatment.
Anybody with information is asked to contact Gurranabraher Garda Station at 021-4946200.