SYDNEY (AFP) - Four Australian sailors were allegedly involved in a bizarre "farewell ceremony" in which a colleague was sexually assaulted with a rubber chicken, in the latest scandal to rock the military, reports said on Tuesday.

The man, who cannot be named, was also allegedly smeared with Deep Heat, a menthol liniment, and the sandwich spread Vegemite before the assault.

The incident allegedly occurred onboard HMAS Newcastle to mark the man's last night at sea after a year on the frigate in August 2011, the Defence Department confirmed. Prosecutor Lieutenant-Colonel David Jordan told a court martial the man was aware that something could happen given the "long-standing tradition of playing pranks" on a sailor's last night, The Sydney Morning Herald said.

But instead of some harmless fun, he was allegedly stripped and tied up in front of other sailors and his genitals and buttocks painted in a substance which he believes was a mixture of Deep Heat and Vegemite, it said. He was then assaulted with the rubber chicken before being carried to the shower where a seaman poured a dark liquid on his head, causing skin and eye irritation, the Defence Force Court Martial in Sydney heard.

The four sailors have been charged with offences including sexual intercourse without consent, forceable confinement and assault occasioning bodily harm.

All pleaded not guilty, except for one sailor who pled guilty to a charge of assault occasioning bodily harm over the shower incident.

The Australian military has been rocked by allegations of sexual abuse and cruel initiation rituals in recent years.

The defence force has said it was committed to change, particularly after the so-called Skype scandal of 2011 in which a male recruit filmed himself having sex with a female classmate and streamed it online to other cadets.

That incident triggered a series of reviews which revealed a culture of covering-up, failing to punish perpetrators and hostility towards victims who complained.

An inquiry into sexual and other abuse in the Australian military established in 2012 received 2,400 complaints in its first year.

Last month the defence force admitted it has sacked more than 380 members over the past two years for misconduct, the use of drugs and other offences.