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Pop star Justin Bieber has launched into an extraordinary online rant against his critics, branding them "stupid" and boasting about his wealth and success.

The teen sensation has endured a troubled few weeks after his 10-day trip to London earlier this month descended into chaos and ended with the singer embroiled in a foul-mouthed clash with a photographer.

Many onlookers speculated Bieber is straining under the pressure of his mega-fame and needs professional help, and even the Baby hitmaker himself admitted earlier this week his recent woes were a result of his gruelling schedule and the stress of being apart from his family.

But now he has hit back with a stunning rant on his Instagram.com page in which he mocks Lindsay Lohan's financial problems, brags about his own career, and insists he "doesn't care" if his fans don't believe in him.

In the posting, which has since been removed, Bieber wrote, "Everyone in my team has been telling me, 'keep the press happy' but I'm tired of all the countless lies in the press right now. Saying I'm going to rehab and how my family is disappointed in me. My family is beyond proud, and nothing's been said by them, my grandparents wouldn't know how to reach to press even (if) they did want to so that was a lie and rehab cmon. If anyone believes I need rehab thats their own stupidity lol (laugh out loud).

"I'm 19 with 5 number one albums, 19 and I've seen the whole world. 19 and I've accomplished more than I could've ever dreamed of. I'm 19 and it must be scary to some people to think that this is just the beginning. I know my talent level and i know I got my head on straight. I know who I am and I know who I'm not.

"My message is to believe. My albums could be about anything but my messages have been to never say never and believe, not to believe in me, but to believe in yourself... I honestly don't care if you don't believe in me because I believe in me, and look where that's gotten me so far.

"I'm writing this with a smile on my face and love in my heart. Letting u (you) know first hand how I feel rather than have these story (sic) linger. I'm a good person with a big heart. And don't think I deserve all of this negative press. I've worked my a-- off to get where I am and my hard work doesn't stop here. I'm growing up finding myself while having people watch me and criticise me everyday I think im doing pretty damn good. And to those comparing me to Lindsey Lohan (sic) look at her 2012 tax statements."

Bieber later deleted his comment about Lindsay Lohan and told TMZ he regretted adding the swipe about the actress.

"My post was only up for a few minutes but I realized right away that what I said at the end was wrong and distracted from what I was trying to say," he said. "I immediately deleted it and rewrote it so it would show what I was really feeling and those words are up now."