Former New York City Mayor Rudy Giuliani accused Joe Biden of threatening Sen. Lindsey Graham (R-S.C.) and compared him to the criminal mafia after Biden reacted to the opening of a probe into his Ukraine dealings.

Giuliani, the president's personal lawyer, tweeted the accusation from his social media account on Friday after quoting the candidate's comments that Graham would "regret his whole life."

"This reminds me of Biden's decree to the media to silence me on September 29th," tweeted Guiliani.

"Now a threat to a US Senator. This is getting to be more and more like my old mafia cases," he added. "They sure do sound like crooks."



Biden responded on Friday to the probe of his and his son's activities in Ukraine by saying he was "disappointed" and "angered."

The Democratic frontrunner claimed that Graham was under the thumb of President Donald Trump and his allies because he knew that he would not be re-elected if he countered the president.

"Lindsey is about to go down in a way that I think he's going to regret his whole life," he said to CNN's Don Lemon.

Giuliani took that to be a threat against Graham.

The investigation will try to uncover whether Biden abused the power of the vice presidency in order to benefit his son, Hunter Biden, who worked for a Ukrainian energy company at a time when the Obama administration had power influence in the country.

Giuliani has alleged that Ukrainian prosecutors who could corroborate these claims were being kept out of the country by the State Department.

Here's more on the Ukraine scandal: