The FBI on Monday raided the office and hotel room of Michael Cohen, President Donald Trump's personal attorney, seeking information about a $130,000 payment the lawyer made to porn star Stormy Daniels shortly before the 2016 election, sources said.

The search warrants were sought and executed by FBI agents and federal prosecutors in New York in coordination with special counsel Robert Mueller's team after an initial referral from Mueller's office.

The FBI also raided Cohen's suite at the Regency Hotel on Manhattan's East Side, where he is believed to be staying while his home undergoes renovations. "They are still here," a doorman said late Monday afternoon.

Several law enforcement officials confirmed the search of Cohen's office was not the work of Mueller's prosecutors. It involves a matter that the Mueller team came across, which the team concluded did not fall under its mandate and passed on to the U.S. attorney's office in Manhattan.

Legal sources familiar with the nature of the search said it involved the $130,000 payment to Daniels, who alleges that she had an affair with Trump. The sources did not say whether it might have also involved other matters.

The White House and Cohen have denied the president had an affair with Daniels.

Trump unleashed a furious assault on Mueller later Monday, saying of the raid, "It's an attack on our country ... what we all stand for."

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"It's a disgraceful situation," the president said, calling Mueller's team biased and riddled with conflicts of interest. "I have this witch hunt constantly going on."

A person familiar with the matter told NBC News that this was not a subpoena requesting documents from Cohen. Instead, the source said, this was a court-authorized search, which means there was sufficient probable cause for a federal judge to agree that a search involving the president's personal attorney could occur without any advance notice to Cohen.

"Today the U.S. Attorney's Office for the Southern District of New York executed a series of search warrants and seized the privileged communications between my client, Michael Cohen, and his clients," Cohen's lawyer, Stephen Ryan, said in a statement. "I have been advised by federal prosecutors that the New York action is, in part, a referral by the Office of Special Counsel, Robert Mueller."

Ryan added, "The decision by the U.S. Attorney's Office in New York to conduct their investigation using search warrants is completely inappropriate and unnecessary. It resulted in the unnecessary seizure of protected attorney-client communications between a lawyer and his clients. These government tactics are also wrong because Mr. Cohen has cooperated completely with all government entities, including providing thousands of non-privileged documents to the Congress and sitting for depositions under oath."

When asked for comment and to confirm the raids, Dawn Dearden, a spokeswoman for the U.S. attorney's office in New York, declined to comment.

Last week, Trump broke his silence on the Daniels matter, saying he was not aware of the payment made by Cohen to Daniels days before the 2016 election.

Trump also said he did not know where the $130,000 came from. Cohen has said it came out of his own pocket. Asked why Cohen had paid Daniels, Trump replied, "You'll have to ask Michael Cohen. Michael is my attorney."

The New York Times, which was the first to report the search of Cohen's office, said it involved several other topics besides the Daniels payment.

There is a pending complaint filed with the Federal Election Commission by the group Common Cause, alleging that the payment to Daniels by the Trump campaign violates the Federal Election Campaign Act. Common Cause also forwarded a copy of its complaint to Deputy Attorney General Rod Rosenstein, who is overseeing the Mueller probe, and the DOJ's Criminal Division and Public Integrity Section, requesting a criminal investigation.

Both the FEC and the Justice Department have jurisdiction over certain campaign laws, but the department can additionally prosecute campaign act violations involving false information provided to the commission.

The adult film star has also sued the president to void the nondisclosure agreement arranged by Cohen, alleging that it is invalid because Trump never signed it. She has described it as a "hush" agreement intended to buy her silence before Election Day.

She has also offered to give back the money she was paid so she can speak freely about the alleged affair — she said on "60 Minutes" recently that the two had sex once in 2006 — and release any text messages, photos and videos she might have.

Cohen also is reportedly a key figure in Mueller’s probe into Russian meddling in the 2016 election and the purported collusion between the Trump campaign and the Kremlin.

Mueller has also examined the role Cohen played in important events related to the Russia probe, particularly a Trump real estate deal in Moscow and a peace proposal for Ukraine described as Russia-friendly and delivered to Cohen by a Ukrainian lawmaker a week after Trump took office, according to The Washington Post.

In October, Cohen was questioned by congressional investigators digging into alleged Russian meddling in the 2016 election, NBC News previously reported. Cohen was grilled over the scuttled plan to build a Trump Tower in Moscow and emails he received in 2015 from Felix Sater, a former Trump associate, about the real estate deal.

Cohen downplayed those conversations, in which Sater bragged about his access to top Kremlin officials, saying it was about "a real estate deal and nothing more." Adam Schiff of California, the top Democrat on the House Intelligence Committee, described Cohen as "fully cooperative with the investigation."