Biebermania has broken out in the Beatles' home city and the teenage pop star is trapped in his hotel.
Thousands of screaming fans discovered where Justin Bieber was staying and swarmed the hotel early on Thursday (10Mar11).
Local cops are so concerned about the situation spiralling out of control, they've asked the singer's tour manager to make sure no one interacts with the crowd.
A source tells Tmz.com that authorities fear a "riot situation" if Bieber or anyone from his crew even waves from a window, and they have threatened to arrest anyone who doesn't take them seriously for inciting a riot.
The Baby hitmaker is in the city to perform at the Echo Arena on Friday (11Mar11).
In a tweet to fans on Thursday, the singer wrote, "This is crazy. There are, like, thousands of people out there. love everybody but gonna try and get some sleep. please don't scream."