Federal investigators executed a search warrant at the home and office of former New York City mayor and Trump attorney Rudy Giuliani on Wednesday, sources familiar with the matter told News 4 New York.

Prosecutors have been probing Giuliani's conduct in relation to Ukraine in recent years, looking into both his alleged lobbying on behalf of powerful interests there, as well as his purported efforts to obtain damaging information on President Biden. The full scope of the investigation is unclear, but it at least partly involves Giuliani’s Ukraine dealings, law enforcement officials have told the AP.

A computer, a cellphone and an iPad were seized by investigators at Giuliani's home, a source said, while other electronics were seized at his office. It was not known precisely why law enforcement obtained the warrant. The warrants, which required approval from the top levels of the Justice Department, signify that prosecutors believe they have probable cause that Giuliani committed a federal crime — though they do not guarantee that charges will materialize.

A third search warrant was served on a phone belonging to Washington lawyer Victoria Toensing, a former federal prosecutor and close ally of Giuliani and Trump. Her law firm issued a statement saying she was informed that she is not a target of the investigation.

The New York Times first reported the search; NBC News has confirmed it was executed Wednesday morning at his Manhattan apartment.

Giuliani has steadfastly denied any wrongdoing in his Ukraine dealings, and did not immediately respond to messages from NBC News. He tweeted Wednesday afternoon that he would appear on a New York City radio station and make a statement, but then missed that appearance and deleted the tweet.

Giuliani released a statement through his attorney Robert Costello that said the search warrants executed in the raids "involve only one indication of an alleged incident of failure to register as a foreign agent," a claim that Giuliani has denied. The federal Foreign Agents Registration Act requires people who lobby on behalf of a foreign government or entity to register with the Justice Department. The once-obscure law, aimed at improving transparency, has received a burst of attention in recent years — particularly during Mueller’s probe, which revealed an array of foreign influence operations in the U.S.

Costello said investigative documents mentioned John Solomon, a former columnist and frequent Fox News commentator with close ties to Giuliani, who pushed baseless or unsubstantiated allegations involving Ukraine and Biden during the 2020 election.

Contacted Wednesday, Solomon said it was news to him that the Justice Department was interested in any communications he had with Giuliani, though he said it was not entirely surprising given the issues raised in the impeachment trial.

“He was someone that tried to pass information to me. I didn’t use most of it,” Solomon said of Giuliani. “If they want to look at that, there’s not going to be anything surprising in it.”

Giuliani accused federal authorities of a “corrupt double standard,” invoking allegations he’s pushed against prominent Democrats, and said that the Justice Department was “running rough shod over the constitutional rights of anyone involved in, or legally defending, former President Donald J. Trump.” The statement also claimed that Giuliani had offered to cooperate.

"The electronics taken are, also, replete with material covered by the attorney client privilege and other constitutional privileges," the statement read. "The warrant served on Mr. Giuliani's law office is another disturbing example of complete disregard for the attorney client privilege protected by the Sixth Amendment to the Constitution."

Giuliani's son Andrew was outside his father's apartment later in the afternoon, seemingly enraged at what had transpired.

"Enough is enough ladies and gentlemen. We cannot stand for this this anymore," he said. "Any American, whether you are red or blue, should be extremely disturbed by what happened here today, b the continued politicization of the Justice Department. This is disgusting, this is absolutely absurd ... If this can happen to the president's lawyer, then this can happen to any one of us."

Bernie Kerik, who served as New York City’s police commissioner during the Sept. 11 attacks and is a longtime Giuliani friend, said the former mayor called him as agents were searching his home on Wednesday morning. Kerik, who was pardoned by Trump for felony convictions that put him behind bars for three years, declined to describe his friend’s mood or reaction, but expressed alarm at the raid, saying agents “shouldn’t have been there in the first place.”

“I think it’s extremely concerning,” he said.

A Justice Department spokesperson did not immediately respond to a request for comment. The U.S. Attorney’s office in Manhattan and the FBI’s New York office declined to comment.

Giuliani, the former U.S. Attorney in Manhattan, served as the city's mayor from 1993 to 2001, and was once celebrated for his leadership after 9/11. But the 76-year-old is better known in recent years for his work as President Donald Trump's personal attorney.

The search warrant steps up the pressure on Giuliani, who was already facing the possible loss of his New York law license over comments he made prior to the Capitol riots in January. The dual searches sent the strongest signal yet that he could eventually face federal charges.

Last December, federal prosecutors discussed whether to make a legal request for Giuliani’s electronic communications, NBC News reported. Prosecutors for the Southern District of New York were in contact with Justice Department officials in Washington about gaining access to his emails.