POLICE have charged a teenager with murder after the death of a 32-year-old man, found fatally wounded in a Fremantle laneway early Wednesday morning.

Randall Lee Duncan of no fixed address, but known to move around Fremantle, died shortly after he was found about 7am on Wednesday.

Police charged an 18-year-old Spearwood man overnight with his murder. The teenager will appear in Fremantle Magistrates Court this morning.

Police immediately cordoned off the alleyway between Collie and Nairn streets after Mr Duncan was seriously assaulted and suffered fatal injuries in the attack.

Police said he died by the time ambulance officers arrived.

A walker taking a shortcut through the laneway made the grim discovery about 7am. Mr Duncan had visible wounds to his body but police would not detail the exact nature of the injuries yesterday, saying a conclusive cause of death would not be known until a post mortem later this week.

Police were yet to establish a timeframe as to when the man was assaulted, Det Sen-Sgt Hindriksen said yesterday.

"He could have been there for some time, so if anyone was in the vicinity in the last several hours, we'd like them to come forward.," he said.

coxn@sundaytimes.newsltd.com.au Follow Nicole Cox on Twitter: @Nic_Coxy