"Britney received some anonymous death threats over the phone and in the mail, and her worst fear is a kidnap plot against Sean or Jayden. She's been having terrible nightmares ever since then and she wakes up in the middle of the night crying out for her boys," a source told Britain's Look magazine.
The source added: "She told her head of security and he thinks it's a lone stalker. Her paranoia has reached fever pitch and she's wracked with fear."
The 27-year-old star"s eagerly anticipated ''Circus'' tour kicked off earlier this month, reports The China Daily.