Katy Perry has paid tribute to Justin Bieber by dressing up in a purple hoodie.

The pop songstress saw the Canadian in concert last night (October 3) in Los Angeles and it seems like she went to the gig in fancy dress.

The 'Wide Awake' star posted an image of herself with a number of others all dressed up in purple hoodies, along with the caption:

"WE ARE BELIEBERS!"

She had earlier tweeted about her musical week, which had also include The Black Keys. Perry said:

"Last night I saw The Black Keys, tonight I saw Bieber. I think my musical week is complete."