US President Donald Trump has reprised his angry attacks on law enforcement following FBI raids targeting his personal lawyer that were related to a federal investigation into possible collusion by Trump campaign aides with Moscow.
In two brief Twitter messages on Tuesday, Trump lamented that "attorney-client privilege is dead" and denounced a "total witch hunt", apparently restating his long-held view of Special Counsel Robert Mueller's investigation. He did not elaborate.
FBI agents executed a series of search warrants on Michael Cohen's office and home on Monday, law enforcement officials said. One source said Cohen was under investigation for activity including possible bank and tax fraud and possible campaign law violations.
The searches, which Trump denounced on Monday as disgraceful, were a dramatic new development in a series of probes involving associates of the Republican president.
"The raid is seismic," Democratic US Senator Richard Blumenthal, a former US attorney, told MSNBC on Tuesday, adding that such searches by the Federal Bureau of Investigation indicate the possibility that a crime was committed.
Monday's events renewed concerns that Trump could try to act against Mueller, who was appointed last year by the Justice Department to investigate alleged Russian meddling in the 2016 election and potential collusion by Trump's campaign. Critics have said that if Trump tried to remove Mueller it would amount to interference in the investigation.
"It would be suicide for the president to want to talk about firing Mueller. The less the president said on this whole thing, the better off he would be, the stronger his presidency would be," Republican US Senator Chuck Grassley said in an interview on the Fox Business Network.
Grassley is chairman of the Senate Judiciary Committee, which is among congressional panels conducting their own Russia probes.
Frank Montoya, a former senior FBI official, said it was extremely rare for the bureau to get the authority to search a lawyer's office, let alone a residence.
"No question, a search warrant for a lawyer is an extraordinary act," he told Reuters. "Factor in that, in this instance, it was the president's own attorney. Unprecedented."
Montoya said the warrant regarding Cohen would have required rigorous scrutiny above and beyond the normal warrant process.
"Everyone involved in this process, including the judge who signed the warrant, understood the scrutiny that would follow its execution," he said. "As such, everyone in the process would have done their damnedest to make the warrant as bulletproof as possible."
Cohen's lawyer, Stephen M. Ryan, said on Monday prosecutors seized communications between Cohen and his clients based in part on a referral by Mueller.
Moscow has denied US intelligence agencies' findings that it meddled in the 2016 presidential campaign and sought to tilt the race in Trump's favour. Trump has denied any collusion by his campaign.
Cohen has come under scrutiny over a $US130,000 payment he made shortly before the 2016 election to adult-film actress Stormy Daniels, who has said that she once had sex with Trump and was paid to keep quiet about it. Last week, Trump said he did not know about the payment.