Trump angrily denounced the Democratic-led hearing as a witch hunt.

President Donald Trump told staff from the U.S. mission to the United Nations on Thursday he wanted to know who provided information to a whistleblower on his phone call with Ukraine's president, likening them to a spy, two newspapers reported.

"I want to know who's the person who gave the whistle-blower the information because that's close to a spy," Trump was quoted as saying by the New York Times and Los Angeles Times.

"You know what we used to do in the old days when we were smart? Right? The spies and treason, we used to handle it a little differently than we do now," the Los Angeles Times reported.

The Los Angeles newspaper said it was given a recording of Trump's remarks by a person who attended the event in New York. The New York Times said its source was briefed on the comments and took notes.

Trump spoke on Thursday as a House of Representatives committee heard testimony from the acting U.S. director of national intelligence on a whistleblower complaint about efforts by Trump to solicit the Ukraine government's help to investigate Democratic presidential hopeful Joe Biden whose son worked in Ukraine.

Upon arriving back in the Washington area later, Trump angrily denounced the Democratic-led hearing as a witch hunt.

The whistleblower report has triggered a controversy and prompted House Speaker Nancy Pelosi, a Democrat, to launch a formal impeachment inquiry this week into the Republican president.