THE unidentified body of a suspected murder victim who died about a year ago has been discovered by cleaners in a Sydney home.

The gruesome discovery was made on Greendale St in Greenwich, a harbourside suburb on Sydney's lower north shore, after the owners hired cleaners to clean the property, on Tuesday.

A NSW Police spokesperson told news.com.au the death was believed to be suspicious because of "something found on the body" but could not yet provide further details about what that was. It's been reported the body appeared to have been "mummified".

The gender and age of the person have not yet been determined but a post mortem is being carried out.

News.com.au understands the alleged victim was not the occupant of the home. According to police, the tenant who lived there, locally named as Bruce Roberts, died a year ago.

According to ABC, detectives are investigating whether Mr Roberts, whose parents owned and lived in the property for 40 or 50 years, had something to do with the death.

Bob and Gayle Meagher have lived next door for 20 years and told ABC, Mr Roberts was a loner, a hoarder and a recluse.

"It's creepy and sad, it's just awful that it's next door, very unpleasant," Mrs Meagher said.

"He was paranoid about security around the home and had barbed wire."

The owners had reportedly believed the property was vacant following the tenant's death - until sending cleaners there this week.

"It's believed the body has been at the home for a considerable time and a post mortem is being conducted this afternoon to establish the cause of death and gender," a police statement read.

Officers from North Shore Police Area Command have established a crime scene "which is continuing to be forensically examined".

"An investigation has been launched in an attempt to identify the circumstances surrounding the death, with local police being assisted by detectives from the State Crime Command's Homicide Squad," the police statement continued.

Police are urging anyone who may know the identity of the deceased, or who has information that may assist, to come forward.

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megan.palin@news.com.au | @Megan_Palin