US President Donald Trump turned the power of the White House against the news media, escalating his attacks on journalists as "the enemy of the people" while his press secretary barred several news outlets from his briefing.

In a speech to the Conservative Political Action Conference on Friday, Trump criticised as "fake news" organisations that publish anonymously sourced reports that reflect poorly on him. 

The President also berated members of his own Federal Bureau of Investigation (FBI) as "leakers" who he said were putting the nation at risk, the New York Times reported.

And in a series of Twitter posts, he assailed the FBI as a dangerously porous agency, condemning unauthorized revelations of classified information from within its ranks.

Hours after Trump's speech, White House Press Secretary Sean Spicer barred journalists from The New York Times and several other news organisations from attending his daily briefing.

Trump's barrage against the news media continued well into Friday night. "FAKE NEWS media knowingly doesn't tell the truth," he wrote on Twitter, singling out The Times and CNN. "A great danger to our country."

Trump's attacks on the press came as the White House pushed back on a report by CNN that a White House official had asked the FBI to rebut a New York Times article last week detailing contacts between Trump's associates and Russian intelligence officials. 

The report asserted that a senior White House official had called top leaders at the FBI to request that they contact reporters to dispute the Times's account.

Trump repeated his assertion that the "fake" news is the "enemy of the American people" during the conference at the Gaylord National Resort and Convention Centre, just south of Washington. 

"It doesn't and never will represent the people, and we're going to do something about it."

Trump also zeroed in on the use of unnamed sources. "I'm against the people that make up stories and make up sources."

"They shouldn't be allowed to use sources unless they use somebody's name. Let their name be put out there," he said.

Meanwhile, Spicer during a briefing at his office said that the White House would relentlessly counter coverage it considered inaccurate. 

"We're just not going to sit back and let, you know, false narratives, false stories, inaccurate facts get out there," he said, according to reports.

The Times, CNN, BuzzFeed News, The Los Angeles Times, Politico, the BBC, The Huffington Post and the Guardian were shut out of the briefing.

Conservative media organisations like Breitbart News, The Washington Times and One America News Network were allowed to attend the conference. Journalists from ABC, CBS, The Wall Street Journal, Bloomberg and Fox News also attended.

However, reporters from The Associated Press and Time magazine chose not to attend the briefing in protest of the White House's actions. The Washington Post did not send a reporter to the session.

"Nothing like this has ever happened at the White House in our long history of covering multiple administrations of different parties," Dean Baquet, the executive editor of The Times, said. 

Marty Baron, the Post's editor, called Spicer's decision "appalling."

"Apparently this is how they retaliate when you report facts they don't like," CNN said.

Asked during the gaggle whether CNN and The New York Times were blocked because the administration was unhappy with their reporting, Spicer responded: "We had it as pool, and then we expanded it, and we added some folks to come cover it. It was my decision to expand the pool."

"The Wall Street Journal strongly objects to the White House's decision to bar certain media outlets from today's gaggle," a Journal spokesman said. 

Politico editor-in-chief John Harris said that "selectively excluding news organizations from White House briefings is misguided."

The White House Correspondents' Association, which represents the press corps, also protested the decision.