Justin Bieber's 19th birthday celebrations in London went flat as he admitted on Twitter that it was his "worst birthday".

The Canadian singer, who celebrated his birthday yesterday (Friday, March 1st) in the UK capital, had previously seemed excited about his plans to mark the occasion.

Earlier in the day, he tweeted: "Gonna be fun tonight. Thanks to everyone for all the birthday wishes. 19! (sic)"

He also added: "Big night ahead." But in the early hours of Saturday morning, he tweeted: "Worst birthday."

E! reported that Bieber hosted a circus-themed party at posh Mayfair club Cirque du Soir, but quickly left following a confrontation between his guests and the venue's security staff.

The singer reportedly headed straight back to his hotel after the incident. A hashtag #BeliebersHatePaparazzi is now trending on Twitter.