A man has been arrested on suspicion of murder after a 64-year-old man died following reports of an assault.
South Wales Police said officers were called to reports of a serious assault in Belmont Walk, in the Butetown area of Cardiff, at just after 09:00 GMT.
A 64-year-old man has died, the force later confirmed, with a 38-year-old man arrested on suspicion of murder.
Det Ch Insp Matt Davies said it would “cause shock to the close-knit community”, and appealed for witnesses.
“I want to assure the public that an early arrest has been made and we are not looking for anyone else in connection with the incident,” he added.
Officers closed local roads around Cardiff Bay and pedestrians were asked to avoid the area during the investigation.