Gardai arrested a man in his 40s and a woman in her 30s this morning.
They're being detained at Pearse Street Garda Station.
At around 11am yesterday morning gardaí were called to an incident at Markievics House on Townsend Street.
A man in his 50s was found with a stab wound and taken to St James' Hospital where he was later pronounced dead.
Gardaí have not yet launched an official murder investigation as they are awaiting the results of a post mortem which will take place this afternoon.
They say they are investigating all of the circumstances surrounding the death and that the scene remains sealed off.