The Australian Defence Force was called in to dispose of an unexploded military device found at Port Beach on Friday morning.

A representative at nearby restaurant Coast Port Beach said the item — an old, unexploded military marine marker — was later detonated far out to sea.

“My understanding is that they took it offshore and blew it up, it was very, very loud,” she said.

WA Police were first called to the North Fremantle beach just before 8am after reports of a suspicious item near the shore.

Worried it might be hazardous, officers cordoned off the area and called in the ADF’s joint explosive ordnance team to dispose of it.

Marine markers are devices dropped from ships into the ocean to create a highly visible reference point on the sea surface.

Defence routinely assists state and territory police with the recovery and disposal of suspected unexploded military ordnance found in public areas.

Beachgoers were urged to stay away from the cordoned-off area while authorities personnel dealt with the item.

The ADF has not confirmed whether the marine marker was taken offshore and detonated, despite the reported explosion.