UPDATED 3pm: "Bieber fever" has swept into Melbourne.
The pop star arrived in the city on Sunday after departing Malaysia, where he performed at the MTV World Stage Live on Saturday.
"Hate these long flights, but worth it to see my fans in Australia," Bieber tweeted.
The teen idol is in Australia for a three-day tour to promote his new album Believe.
Security is on lockdown with Bieber's record label Universal offering few details about the trip, which will include appearances on Australia's Got Talent, Sunrise and Channel [V].
Despite the secrecy surrounding the star's whirlwind tour of Melbourne and Sydney, it didn't take his dedicated fans long to figure out where Bieber was hiding out after arriving Down Under.
Fans, mostly teenage girls, have camped outside The Olsen Hotel on Chapel Street in South Yarra, where it's believed Bieber, 18, is staying.
A crowd started gathering at the stylish hotel after news of Bieber's arrival was broadcast on social networking site Twitter.
"THE OLSEN HOTEL LOCATED IN CHAPEL ST! AUSSIE BELIEBERS GET DOWN THERE!" one fan tweeted on Sunday afternoon.
"Justin's at the Olsen Hotel but fans can't go in and he won't come out. You could always climb the walls like spiderman or wait it out," another fan tweeted in excitement.
The first photographs of Bieber in Australia have also appeared online. A series of six photos on fan website justinbieberzone.com, show the teen pop star, dressed in a grey hoodie, posing with fans at what appears to be an airport.
In one of the photos, a Victorian police officer is depicted in the background.
Another snap on photo-sharing site Instagram shows Bieber walking through the foyer of The Olsen.
Last time the Canadian star visited - in April 2010 - it was pandemonium. A planned free concert, put on by the Seven Network's Sunrise program at Sydney's Circular Quay was cancelled due to overcrowding.
As hordes of teenagers surged forward, things got so dangerous that Bieber pleaded with them to go home.
The television network is taking no chances this time, promising beefed-up security to safeguard Bieber's Sunrise appearance on Wednesday morning.