A man has been charged with murder after allegedly fatally injuring another man in South Australia.

Police found a 65-year-old man with serious injuries at an apartment complex in Bond Street, Mount Gambier, five hours southeast of Adelaide, after reports of a "disturbance" at 3pm yesterday.

He was taken to hospital and died a short time later. 

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A 65-year-old man was arrested at the scene.

Police believe the two men were known to each other.

The man, who has no fixed address, was charged with murder and will appear in Gambier Magistrates Court today.

Police are not searching for other suspects in relation to the alleged crime.