Talk about Bieber Fever pitch! Justin Bieber has been trapped inside his Liverpool hotel room after fans turned out in droves to catch a glimpse of the teen idol.

Police have warned the 'Never Say Never' star that he and his team must stay inside their hotel room and away from the balcony on their suite, fearing a "possible riot situation," according to The Hollywood Reporter.

Upon seeing the throngs of adoring fans crowded outside the hotel, Bieber tweeted, "THIS IS CRAZY!"

Check out the photos of Bieber madness in Liverpool inside.