Sydney  - Police in Western Australia on Saturday charged the father of 4-month-old Zach O'Kane with murder after the baby's body was found in a national park.

John O'Kane, 40, led police to the makeshift grave after his arrest on Friday.

The alarm was raised when O'Kane failed to return the child to his estranged wife after an access visit.

At the time of his arrest, O'Kane was suffering from a self-inflicted stab wound that needed hospital attention. (dpa)