Police are investigating the death of a man who had been assaulted at Milikapati on the Tiwi Islands on Sunday, NT Police said.

Police director of communications Mark Wilton said a statement that about 10.40am Sunday St John Ambulance received a call reporting a 59-year-old man had been assaulted by another man and was unconscious.

He said local clinic staff performed CPR but the man was declared dead at the scene.

Officers arrested a man who they found at an undisclosed location.