Security services say the targets included Federation Square, Flinders Street Station and St Paul's Cathedral.
A plot to attack prominent sites in Melbourne with a series of bombs on Christmas Day has been foiled by Australian security services.
Two of seven people initially arrested in raids on Thursday night and Friday morning in Melbourne - a 26-year-old man and a 20-year-old woman - have been released without charge.
Five men, aged between 21 and 26, remained in custody over the plot which has been described as "an imminent terrorist event" inspired by Islamic State.
'IS-inspired' Melbourne Christmas Day terror plot foiled