Federal investigators wiretapped the phone lines of president Donald Trump's lawyer Michael Cohen before the FBI seized records and documents in a raid last month on his offices, hotel room and home, NBC News reported on Thursday.
NBC, citing sources familiar with legal proceedings involving Mr Cohen, said it was unclear how long the wiretap had been authorised, but it was in place in the weeks before the April 9 raids in New York targeting the lawyer. At least one call between a phone line associated with the lawyer and the White House was intercepted, NBC quoted one source as saying.
The raids were part of a federal criminal investigation of Mr Cohen in New York in part over a $130,000 payment he made to adult film star Stormy Daniels a month before the 2016 presidential election to keep her quiet about a sexual encounter she said she had with Mr Trump in 2006.
Earlier on Thursday, the president said on Twitter that Mr Cohen was reimbursed for that payment through a monthly retainer, not campaign funds, to stop "false and extortionist accusations" Ms Daniels has made about a sexual relationship with the president.
The wiretapping of Mr Cohen, if confirmed, would represent the latest ominous development for the president, who faces legal difficulties on several fronts. The investigation of him is an offshoot of the ongoing probe by special counsel Robert Mueller into potential collusion between Mr Trump's 2016 campaign and Russia and whether the president has unlawfully sought to obstruct the investigation. Russia and Mr Trump deny any collusion.
Ms Daniels also has filed two lawsuits against the president.
It was not immediately clear when the warrant for surveillance was obtained or what evidence the Federal Bureau of Investigation had to support its request.
Rudy Giuliani, the former New York mayor who is a member of Mr Trump's legal team, told the Washington Post that, if true, the wiretaps would be "not appropriate", according to a Twitter post by a Post reporter.
"You mean, I call up my lawyer and the government is wiretapping him?" Mr Giuliani asked in comments to the Post. "... They've already eviscerated the attorney-client privilege. This would make a mockery of it."
Attorney-client privilege generally shields communications between a lawyer and a client.