A convicted murderer accused of plotting to castrate and kill Justin Bieber has been moved to solitary confinement behind bars after outlining new plans to blow up one of the pop sensation's concerts in a letter to a U.S. TV station.



Dana Martin, who is currently serving two life sentences in a New Mexico prison for the 2000 rape and killing of a 15-year-old girl, was said to have been the brains behind a grisly 2012 plot to torture and murder the pop star, recruiting fellow inmate Mark Staake to carry out the slaughter upon his release with his nephew Tanner Ruane.



The plot was foiled after Staake was arrested in Vermont on outstanding warrants, prompting him to come clean about Martin's plan and turn in his nephew, who was busted in New York in November, when the singer was in the Big Apple as part of his Believe tour.



Now Martin has revealed details about another Bieber murder plot in a message he sent to TV bosses, claiming he would be hiring a new assailant to carry out the crime.



In the note, the prisoner wrote, "I arranged for another hit man. This new hit man will place an explosive device... at a live performance, killing everyone on stage and quite a few in the audience."



The letter was handed to authorities and prison bosses have since withdrawn all of the convicted murderer's communication privileges and placed him in solitary confinement as they investigate the latest accusations.



The chilling news will add to Bieber's worries as he pushes on with his European tour following a tumultuous 10 days in the U.K., during which he clashed with the paparazzi, fought with bouncers at a nightclub as he celebrated his 19th birthday, fell sick onstage and came under fire for turning up late for his opening gig at London's O2 Arena.