An 87-year-old man has died after a suspected assault while going for a morning walk in Queensland's Noosa Heads this morning.

Police said the Noosa local died shortly after emergency crews were called to the scene on Hastings Street about 6am.

Sunshine Coast Detective Inspector Chris Toohey said the man was found with severe facial injuries and lying face up on a boardwalk path. 

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The facial injuries are consistent with an assault, police say.

Local woman Caroline Clark said her friend, who is a nurse, was among the passersby who attempted to help.

"They just stumbled across him as he was lying on the ground," Clarke said.

Clarke said her friend attempted CPR, but the man could not be saved.

Police apprehended a 27-year-old man less than 100 metres from the crime scene, Toohey said.

The man was in custody and assisting police with their enquiries but no charges had been laid, he said on Sunday afternoon.

Clarke said she saw the arrest take place.

"This guy was running around naked and (seemed to be a) suspect," she said.

The suspect and his alleged victim are not believed to be known to each other.

Police have now launched a homicide investigation, with officers today taping off a large crime scene spanning the carpark and several hundred metres of beachfront.

Police divers were seen scouring the water.

Toohey said police were not yet in a position to comment on whether a weapon may have been used in the alleged attack.

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