Warning: This story contains content that some readers may find disturbing.

A man charged with murder in Queensland's far north cut off the victim's leg as part of an arrangement between the pair, police allege.

Just before 4am yesterday morning, It's alleged a 36-year-old man used a circular saw to cut off a 66-year-old man's leg near Fitzgerald Esplanade in Innisfail, about an hour south of Cairns.

Police now say the amputation was planned as part of a pact between friends.

"During my 34 years of being a police officer, I have never experienced a situation as we are presented with here," Detective Acting Inspector Gary Hunter said.

"We are unable to establish the motive behind the removal of the leg but we can say it's an arrangement between the two people."

9News understands the saw belonged to the 66-year-old and that the men travelled to the park together with the intent to carry out the amputation.

Police allege the 36-year-old Innisfail man helped the older man back to his car, before leaving the area on foot.

But the older man was unable to get back into the car and lost consciousness before two locals on their morning walk found him.

He died before paramedics arrived.

The 36-year-old has been charged with one count of murder.