Bad enough she has to deal with K-Fed, dada Jamie and the entire Circus on tour but now Britney Spears has been receiving mysterious death threats!

Reportedly a stalker has been tracking her every move as the Brit's Big Top travels from city to city.

"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," an insider revealed.

"She's been having terrible nightmares ever since then and she wakes up in the middle of the night crying out for her boys."

Team Britney has intensified security - big time.