WASHINGTON, April 9 (Xinhua) -- U.S. President Donald Trump blasted the ongoing Russia probe on Monday after knowing that his long-time personal lawyer's office was raided by FBI agents who seized documents related to a hush money payment to an adult film actress.

"It's a disgraceful situation," Trump told reporters before a meeting with senior military leaders at the White House, adding that FBI agents "broke into" the office of his lawyer, Michael Cohen, who Trump said is a "good man".

The New York Times reported earlier that federal prosecutors in Manhattan obtained a search warrant after receiving a referral from special counsel Robert Mueller, then raided Cohen's office and seized emails, tax documents, business records and communications between Cohen and Trump.

Prosecutors and agents must convince a judge that they have probable cause of criminal activity and that they believe they'll find evidence of wrongdoing in a search before they are granted a warrant.

But the raid reportedly does not appear to be directly related to Mueller's investigation, which focuses on alleged Russian meddling in the 2016 U.S. presidential election and possible collusion between the Trump campaign and Moscow.

Sharpening his invective, Trump called the sweeping Mueller inquiry "an attack" on the country and what it stands for. "That is really now on a whole new level of unfairness."

The president repeated his claim that "there was no collusion at all," while describing the team of Mueller, a lifelong Republican, as having "the biggest conflicts of interest" he has ever seen and the investigation again as "witch hunt."

Trump stressed that he's not concerned about what the FBI might find, but said "we'll see what happens" when asked if he would fire the special counsel, who reports to Deputy Attorney General Rod Rosenstein.

Cohen's lawyer, Stephen Ryan, told The Times that the search was "completely inappropriate and unnecessary."

Among the documents federal agents seized were those related to Cohen's 130,000-U.S.-dollar hush money payment to Stormy Daniels, an adult film actress who has alleged having an affair with Trump in 2006.

The payment was made to Daniels, whose legal name is Stephanie Clifford, for her silence about the alleged affair, just days before the 2016 U.S. presidential election. Cohen has denied it violated campaign finances laws.

Last week, Trump denied knowledge of the payment. It was the first time that the president has publicly addressed the issue. The White House has said that Trump denies there was a relationship.

Daniels was trying to void a non-disclosure agreement that she signed for the payment, while her lawyer filed a renewed motion on Sunday to depose Trump and Cohen over the matter.

Cohen, who has been Trump's personal lawyer for years, has reportedly a role in several aspects of the special counsel's investigation, which is looking into whether Trump attempted to obstruct the progress.

The special counsel has so far charged 19 people, among whom were several Trump campaign associates that have pleaded guilty to various charges stemming from Mueller's investigation. They are all cooperating with prosecutors but none of the charges directly relate to the collusion allegation.

Analysts say that the raid creates a new legal headache for Trump and his attorneys as they were reportedly considering an interview with the special counsel.

It was reported earlier this month that Mueller told Trump's lawyers that the president is not a criminal target of the Russia probe, but stressed that he remains a subject of the investigation.

CNN reported whether Trump will speak with Mueller under oath or in an informal setting is still being negotiated.