Katy Perry Supports Close Friend Justin Bieber On 'Believe' Tour

Wenn / Twitter

Katy Perry was among the stars who turned out watch Justin Bieber on his 'Believe' as he performed Los Angeles last night.

The 'Part Of Me' singer took friends to see her pal Bieber as he performed his second consecutive night in the California city yesterday (October 3).

"WE ARE BELIEVERS!" Katy Perry tweeted alongside a picture of her and friends dressed up in Justin's trademark purple hoodie.

"Last night I saw the Black Keys, tonight I saw Bieber. I think my musical week is complete," which was later retweeted by the main man himself.

Katy Perry Supports Close Friend Justin Bieber On 'Believe' Tour

Katy Perry was suited and booted to watch Bieber (Twitter)

The Saturdays; Frankie Sandford and Mollie King were also in the audience and shared pictures of the show with their followers on twitter.

"Is it a bird, is it a plane, no it's @JustinBieber!!!" Mollie tweeted, "Bieber Fever!! Oldest people here by a MILE! Hahaha! I feel ancient!"

Katy Perry Supports Close Friend Justin Bieber On 'Believe' Tour

The Saturdays enjoy their time in LA (Twitter)

Justin's first concert for his new "Believe" tour but things didn't go to plan when poor Biebs stopped midway through a number, turned around and promptly vomited on stage.

However last night Bieber put on a spectacular show for fans with a little help from his close friend Carly Rae Jepsen.

Fans were treated to tracks from his new album Believe, including singles 'Boyfriend' and 'As Long As You Love Me' as well as his biggest hits 'Baby'.

The 'Boyfriend' star will head over to the UK next year to perform at the O2 Arena in the capital on February 17 before heading to Manchester to kick off the UK series of shows .

Bieber will now play seven dates across the UK later this year. The jaunt will kick off on February 19 at the Manchester Arena and will conclude on March 4 with at London's O2 Arena.

Justin Bieber Sends Fans Wild On 'Believe' Tour