Photo: © 2010 AAP/DEAN LEWINS

Thousands of teenage girls camped overnight at Circular Quay to catch a glimpse of the pop mega-star.

The 16-year-old heartthrob was supposed to sing three songs in front of the Overseas Passenger Terminal.

But the concert was cancelled after the crowd got out of control, surging and breaking through barriers.

Police say a number of girls fainted, hyperventilated and suffered "crush injuries".  

The dreamy teen eventually sang a song for fans back at the Martin Place studios of Channel 7's Sunrise program, which had organised the concert.

Afterwards, Bieber joined the show's hosts, Mel and Kochie, for a chat.

"You're such a good kid and role model for all young Australian girls, it's just terrific," an excitable Kochie told him.

Bieber apologised for the morning's madness, saying "it get's crazy sometimes".

"I am so sorry that it got out of control ... we don't want anyone to get hurt."

He was also asked about his mum, who helped him become a star when she uploaded clips of him singing to YouTube.

"She's been supportive since day one," he said.