Police are trying to free a woman apparently strapped to a booby-trapped bomb at her home in a wealthy area of Sydney, Australia.

New South Wales police said the 18-year-old woman called them to the house in the suburb of Mosman.

They then evacuated surrounding homes and members of the bomb squad were were called in to examine the device.

"The process demands a high level of skill and must be meticulous," police said.

Police would not comment on reports that the device had been strapped to the woman by someone she did not know, but said the incident was "not being treated as self-harm".

Several nearby streets were closed to traffic, and medical and fire crews were on standby.

Assistant Commissioner Mark Murdoch would not comment on reports the device had been strapped to the woman.

"There's a device in the house in the vicinity of the young woman. That device is still being examined as we speak," he said. "We are treating the device as live until we know otherwise.

"The young lady is fine and doing her best to assist the police to find out exactly what's gone on," he said.