Kevin James Russell was arrested over the alleged murder of 58-year-old Allan Dempsey at a North Wollongong apartment block.

Emergency services were called to a unit on Cliff Road at 7.28pm, where they found the victim unconscious and bloody. He had suffered a serious stab wound to his back, behind his left shoulder.

Ambulance NSW Illawarra duty operations manager Inspector Norm Rees said the victim went into cardiac arrest. He praised police efforts with CPR until paramedics arrived on scene.

​Dozens of onlookers watched by the side of the busy road as Mr Demspey was stretchered out and rushed to Wollongong Hospital by ambulance. Treatment continued for another half an hour, though he was unable to be revived.

Wollongong local area commander Superintendent Joe Cassar said shortly after 7.30pm officers apprehended Russell at an address on Corrimal Street.

He appeared briefly in court Saturday morning but was refused bail.

Forensic officers spent the weekend scouring over crime scenes set up at both the Cliff Road and Corrimal Street locations.

Superintendent Cassar said Strike Force Contay had been established and a number of people were assisting them in their investigations including residents along Cliff Road and other people who were in the area at the time.

He said at this stage there was no suggestion it was a random attack and confirmed the pair knew each other.

Anyone with any information is urged to contact Wollongong Police, or Crime Stoppers on 1800 333 000.

Illawarra Mercury