A notorious Australian serial killer who is serving a life sentence for the slayings of seven backpackers cut off his little finger in his prison cell and attempted to mail it to the country's top court, officials said Tuesday.

Ivan Milat, 64, who was convicted in 1996 of murdering the young travelers, used a serrated plastic knife that came with his meal to sever the finger from his left hand on Monday, a spokesman for the New South Wales state Department of Corrective Services said on customary condition of anonymity.

Milat, who is housed in a maximum security cell at Goulburn Correctional Centre, 125 miles south of Sydney, then placed the severed digit in an envelope addressed to the High Court of Australia and handed it to an officer.

He was rushed to a hospital, but surgeons were unable to reattach the finger, the spokesman said. The killer was returned to prison later Monday and appeared in good health, though he was refusing to eat.

Milat offered no clues as to what his motive was, the spokesman said, adding the incident is under investigation.

"It's the work of a desperate man and Ivan Milat is in the top echelon of desperate people," John Dunthorne, the department's southwest region assistant commissioner, told Australia's 2UE radio Tuesday.

Milat has attempted to mutilate himself before. In 2001, he swallowed three disposable razor blades, and later that year swallowed a spring from the toilet in his cell.

Milat killed three Germans, two Britons and two Australians between 1989 and 1992. Their bodies were later found in shallow graves in a remote forest southwest of Sydney.