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After calling his 19th birthday his "worst birthday," Justin Bieber has taken to Instagram to explain what really went down.

Speaking out about reports that he and his entourage were asked to leave London club Cirque du Soir on Friday, following a disagreement reportedly over the presence of underage guests, Bieber wrote, "The funny moment when people believe I brought underage people to a club."

Bieber referred specifically to a report that his friend Jaden Smith, the 14-year-old son of Will Smith, was turned away from the party. "U think Will is letting his 14 year old in a club, I don't think so," he wrote.

Bieber claimed that the club, which had issued a lengthy statement saying they shut down the party due to his underage guests, invented that story to save face, because he and his crew decided they didn't want to party there anymore because of how they were being treated.

Read More about Justin Bieber's Worst Birthday

"I love how the club wanted to give the press another reason to why we didn't stay at their weak a** club so they wouldn't look bad for me walking in and right back out," Bieber declared on Instagram.

The pop star also explained why he called Friday his "worst birthday." "That was due to dummies pushing over my fans and being overly aggressive."

He added, "Btw it wasn't the worst bday cuz all my friends from back home flew in I was just mad in the moment."

A club spokesperson originally told E! Online, "We, like all clubs in London, operate a strict age policy. As a few of the members of the party were under the suitable age of 18, the security team at Cirque Du Soir, London, clearly explained this rule and refused entry to the club for anyone who could not provide us with adequate proof of age."