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Kris Jenner has called in extra security after a man claiming to have a sex tape of her threatened her with extortion, it has been claimed.

The head of the Kardashian klan was reportedly approached more than a week ago by an unknown man claiming to have footage of her having sex.

An insider reportedly told RadarOnline: "The man has been demanding money from Kris. If he’s not paid, he claims, he’ll release the tape."

The site reports Kris thought it was all a joke to start, but now she's worried he is stalking her.

They added: “He called Kris more than one hundred times in the last seven days, from more than 100 different phone numbers."

The 58-year-old says there is no sex tape, but because of the worrying phone calls, she has called in reinforcements, according to Radar Online.