Liverpool hasn't seen this much tween angst since the Beatles. Right now modern day mop top Justin Bieber is holed up at a hotel in the area with thousands of girls outside his window freaking out and awaiting a glimpse of the pop star. According to TMZ (they've got a photo from the scene), the cops there have warned The Biebs that it could turn into a "possible riot situation" and have threatened to arrest him if he makes himself visible.

The site reports that "the pop star and his entourage have been warned that if Bieb or his team go anywhere near the balcony... they will be arrested immediately for inciting a riot."

London: you are officially on Bieber Fever alert! Long Island experienced an outbreak back in 2009; Bieber took to Twitter to calm his frenzied masses, and his appearance was ultimately canceled after teens trampled each other. Godspeed, London.

UPDATE: Calm down everyone! Justin Bieber was given the all clear and has now waved to his fans, or according to this photo on TMZ, made a little heart with his hands. The police hope this gesture will now make the fans go away.