Bieber, 19, is said to have ordered a 24-hour watch after becoming increasingly fearful that his fans might break into his room, reported Daily Star.
"Justin can't be alone at night right now. He is paranoid about fans breaking into his room, and he hears noises all the time.
"It freaks him out. As well as the ever-present guard in his room and the one outside, he also has two on standby to take over when his men need breaks," a source said.
"Justin is now used to having a guard watch him sleep and he wants the arrangement to continue after the tour finishes. He also begged his mother Pattie to accompany him on most of the concert dates. She was asked to combine her book signing tour with his gigs because he gets so anxious.