A gunman who killed a man and took a woman hostage before dying in a police shoot-out had been acquitted of plotting a terror attack at a Sydney army base years earlier, Australian police said.

Police in Australia have detained five suspects who were allegedly planning a series of Christmas Day bomb attacks in the heart of the country's second largest city.

A senior Melbourne police chief has joined with Jill Meagher’s grieving husband in calling for people not to post anything on social media websites which might prejudice the trial of the man accused of killing her.