Federal prosecutors in Manhattan are reviewing the accusations of extortion and blackmail made by Amazon CEO Jeff Bezos against the parent company of the National Enquirer, a source familiar with the matter told ABC News on Friday.

American Media Inc., which owns the tabloid, was granted immunity from the U.S. Attorney’s Office for the Southern District of New York in December of last year as part of an investigation into the president's former personal attorney and longtime fixer Michael Cohen. Prosecutors are now reviewing whether Bezos’s accusations amount to a violation of that agreement, which required AMI to “commit no crime whatsoever” for three years, according to the source.

A spokesman for the U.S. Attorney’s Office for the Southern District of New York declined to comment.

AMI said Friday it would "promptly and thoroughly" investigate claims made by Bezos of a blackmail and extortion plot against him involving compromising photographs.

Bezos described the claims in a stunning post on Medium Thursday.

The National Enquirer later broke a story that alleged Bezos was having an affair. Bezos questioned whether the report was politically motivated and launched his own investigation into the matter.

In a post titled "No thank you, Mr. Pecker" -- addressing David Pecker, who is the chairman and CEO of American Media Inc., the owner of the National Enquirer -- Bezos said that he was approached with an offer from AMI, saying that "they had more of my text messages and photos that they would publish if we didn't stop our investigation."

Bezos alleges the National Enquirer was attempting to blackmail and extort him using "intimate" photos.

In the Medium posting, Bezos said that the Enquirer offered not to publish the photos in exchange for a public statement from Bezos that the Enquirer's reporting was not politically motivated.

"Of course I don't want personal photos published, but I also won’t participate in their well-known practice of blackmail, political favors, political attacks, and corruption. I prefer to stand up, roll this log over, and see what crawls out," Bezos said in his post on Thursday.

AMI defended its actions in a statement Friday but said it would investigate Bezos' claims.

"American Media believes fervently that it acted lawfully in the reporting of the story of Mr. Bezos," the company said in a statement. “Nonetheless, in light of the nature of the allegations published by Mr. Bezos, the Board has convened and determined that it should promptly and thoroughly investigate the claims. Upon completion of that investigation, the Board will take whatever appropriate action is necessary."