Justin Bieber was to be strangled and castrated as part of a gruesome kidnap plot ordered by an obsessed jailed killer, according to a bizarre court case in the US.

Mark Staake, 41, and his 23-year-old nephew Tanner Ruane from New Mexico were allegedly commissioned by convicted killer Dana Martin to murder four men, including the pop superstar and his bodyguard.

Martin, who met Staake in prison, apparently gave exact details as to how the plot was to play out.

It included the use of a paisley tie - his old calling card - to strangle the victims and the offer of a \$2,500 (£1,600) bounty for each of the men's testicles.

But Staake was arrested in Vermont on November 19 on outstanding warrants for previous offences before any murders could take place, KRQE-13 TV in New Mexico reported.

A day later he was secretly recorded by police on the phone to Ruane, talking about the alleged plot.

The younger man was picked up in upstate New York, as Bieber prepared for performances at Madison Square Garden.

According to court documents, he was found with a pair of pruning shears and documents including the identities of the intended victims.

The 18-year-old star's management team issued a short statement on Wednesday night.

"We take every precaution to protect and insure the safety of Justin and his fans,” it said.

Ruane's mother, Kristin Cashman, told the New York Post the whole case was ridiculous.

"My son was not planning to kidnap or hurt anyone. He has nothing to do with any of this," she said.

"This has got to be some crazy thing Dana Martin made up. Everything about it is made up."

Martin, who is described as being obsessed with the Canadian singer, is also reported to have told the authorities about the alleged plot.

Staake and Ruane face two counts of conspiracy to commit murder and two counts of conspiracy to commit aggravated battery.