Federal investigators executed search warrants on former Mayor Rudy Giuliani’s Upper East Side apartment and his Manhattan office on Wednesday, as part of a criminal probe into his involvement with Ukraine, according to news reports.

Giuliani’s electronic devices were seized as part of the searches, the New York Times first reported.

Giuliani had been under federal investigation for his business dealings in Ukraine while he served as the personal attorney for former President Donald Trump, according to the Associated Press. The investigation involves whether he “illegally lobbied the Trump administration on behalf of Ukrainian officials and oligarchs in 2019,” the Daily Beast reported.

Giuliani pressed Ukrainian officials to investigate President Joe Biden and his son Hunter, and also met several times with a Ukrainian politician “who released edited recordings of Biden in an effort to smear him before the election,” according to the AP.

Giuliani’s attorney, Robert J. Costello, called the searches "legal thuggery" in a statement provided to the Times. "Why would you do this to anyone, let alone someone who was the associate attorney general, United States attorney, the mayor of New York City and the personal lawyer to the 45th president of the United States.”

The search of Giuliani’s apartment and office is seen as a significant step in the criminal investigation -- CNN noted that “it is unusual for prosecutors to execute a search warrant on a lawyer, although Manhattan federal prosecutors have done so before, most notably in recent years against another former lawyer for Trump, Michael Cohen.”

Trump appointees within the Justice Department blocked Manhattan prosecutors who sought a search warrant on Giuliani last year, the New York Times reported, and the investigation stalled in the final months of Trump's term, as Giuliani represented Trump in his attempt to overturn the results of the presidential election. The investigation intensified after Merrick Garland was confirmed as US Attorney General last month and the Justice Department “lifted its objection” to the search warrant.

Giuliani has previously said the investigation was “pure political persecution.”

A spokesperson for the Justice Department declined to comment Wednesday.