New South Wales's top counter-terrorism officer says the police don't know what message al-Qaeda is trying to send by publishing a photo of Sydney Opera House in one of its online magazines.
Assistant Commissioner Peter Dein says he became aware of the photo, which is not accompanied by any text, on Tuesday.
Mr Dein says he is not concerned by any imminent terror threat.
The photo is on the same page that features a story on bomb making, the ABC reports.
Assistant Commissioner Dein says it is hard to interpret what the photo is meant to do as the picture has been published without any written explanation.