Britney Spears has threatened to cancel her eagerly anticipated Circus tour - which kicked off only last month - after receiving a string of anonymous death threats by phone and mail.
The If U Seek Amy singer is said to fear for the lives of her sons Sean Preston and Jayden James, who are both accompanying her on the tour.
A source told Look magazine: "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.
"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."
Britney has also apparently been left distraught after being accused of miming during her recent tour performances.
Music-News.com quoted a source as saying: "Britney is under so much strain, what with relentless performing, the bad reviews and the worry over her boys. It all got too much and she screamed at her team, 'I can't do this any more, why are you all torturing me?' She ran out of the room crying."
Britney is due to arrive in the U.K. on the 3rd of June for the first of eight dates at the O2 arena, moving to the Manchester's M.E.N. Arena for her final Circus Tour performance.