Kris Jenner is reportedly trying to untangle herself from a sleazy sex-tape extortion plot --and has even had security tightened around her Kardashian Empire.

According to a close family source, last week Jenner was approached by an unknown man claiming to be in possession of a sex tape starring the Keeping Up with the Kardashians momager.

“At first she thought it was a joke, because she knew it couldn’t be real,” the source told Radar. “Obviously she would never allow herself to be taped like that! Initially, she just ignored it.”

Via Radar Online:

“He called Kris more than one hundred times in the last seven days, from more than 100 different phone numbers,” the source revealed. “He uses scrambled cell numbers. He called more than 25 times just yesterday (Sunday) alone!”

“The man has been demanding money from Kris. If he’s not paid, he claims, he’ll release the tape.”

The source then added:

“She thinks he could be following her,” the source confirmed. “She went out to eat and then got a text from him saying ‘Are you enjoying the restaurant? This person knew where she was.

As a result, the insider revealed, “The family has drastically stepped up their security and Kris had no choice but to turn all the information over to law enforcement and to [the family's private investigator] Gavin DeBecker.”

Said the source, “They’re assessing their options. Not surprisingly, everyone is worried.”

The story is still developing....