Australian police have warned teenagers about posting photographs of themselves on social networking sites such as Facebook after a young woman was allegedly murdered by an Internet "friend".

Young people should ensure that only people they know are able to see their pictures and personal details such as their date of birth, school and home address, Detective Superintendent Peter Crawford said.

"I can see no reason why you would want to have a photograph of a teenager or a young child accessible to anybody who wants to look at it on the Internet," Queensland-based Crawford told AFP today.

"It's not just the issue of the photograph. If someone is prepared to put their photograph, then they are generally also putting a lot of other information about themselves on the Internet."

The warning comes after a Sydney man was last week charged with murder after allegedly creating a bogus identity on Facebook and using it to lure 18-year-old Nona Belomesoff to an isolated bushland area.

Photos of Belomesoff taken from her profile have been splashed across Australian newspapers, prompting New South Wales police to warn that too much online data is readily available to the public.

"Don't have a photo of yourself on Facebook. Have photos only open to friends," Detective Superintendent John Kerlatec of the New South Wales police computer crime squad told The Daily Telegraph this week.