A murder inquiry has been launched following the death of a 24-year-old man.
The victim died in the University Hospital of Wales in Cardiff on Sunday morning from injuries he sustained hours earlier.
South Wales Police said the man, who has not been identified, was injured during an incident at an address in Cranleigh Rise, Llanrumney, Cardiff.
The emergency services were called to the property shortly after 1am and the 24-year-old, who was from Cardiff, was taken by ambulance to hospital where he later died.
A 53-year-old man has been arrested on suspicion of murder and is currently in custody at Cardiff Bay police station.
Detective Chief Inspector Dorian Lloyd, who is leading the investigation, said an incident room has been set up at Cardiff Central police station.
"I would like to reassure the community that a full police investigation is currently under way and a 53-year-old man has been arrested on suspicion of murder," Mr Lloyd said.
"We will utilise our extremely strong community links to fully understand the events that led to this tragic death.
"We are appealing to anyone who has any information or who may have witnessed any suspicious activity in the Cranleigh Rise area of Llanrumney to contact South Wales Police on 101 or Crimestoppers anonymously on 0800 555 111."