WASHINGTON (AFP) - US Attorney General Jeff Sessions on Friday (Aug 4) vowed to crack down on government employees who leak classified or sensitive information, after a spate of revelations in the media - many of them unfavourable - about the Trump administration.

President Donald Trump has repeatedly fumed about "illegal leaks" and even lashed out publicly at Sessions for taking what he called a "very weak" position on the issue.

Under pressure, and with some saying his job could be on the line, Sessions responded.

"I strongly agree with the President and condemn in the strongest terms the staggering number of leaks undermining the ability of our government to protect this country," Sessions told a press conference.

Four people have already been charged with "unlawfully disclosing" classified material or concealing contacts with federal officers, he said.

Active leak investigations this year have tripled compared with the number before Trump took office, Sessions added.

"We are taking a stand. This culture of leaking must stop," he said, adding that "we will not allow rogue anonymous sources with security clearances to sell out our country."

'MEDIA SUBPOENAS' UNDER REVIEW

Moves to crack down on damaging leaks did not originate with Trump's administration.

Under his predecessor Barack Obama, whistleblowers and leakers who talked to journalists were prosecuted, and the Justice Department issued subpoenas to reporters to compel them to reveal their sources.

In what could signal an ominous turn, Sessions said his Justice Department was reviewing policies affecting "media subpoenas."

While the administration has respect for the press, "it is not unlimited," he said.

"They cannot place lives at risk with impunity," he added. "We must balance the press's role with protecting our national security."

Deputy Attorney-General Rod Rosenstein fleshed out some details, telling reporters there would be a new, dedicated unit at the Federal Bureau of Investigation that would be "focused on media leaks."

Asked if the Justice Department would rule out prosecuting reporters "for doing their job," Rosenstein said he was not going to comment on "hypotheticals."

Changes to policies concerning the media would only be taken following consultations with representatives of news outlets, he said.

The flexing of judiciary muscle came just hours after yet another stunning revelation leaked to the media: a report by The Wall Street Journal that special counsel Robert Mueller has impaneled a grand jury to investigate Russia's interference with the 2016 presidential election.

Grand jury proceedings are typically secret, and the exposure only highlighted the leaky sieve that Washington has become.

'WE WILL FIND YOU'

A prominent civil rights group warned that clamping down on leakers signaled a crackdown against democracy itself.

"Every American should be concerned about the Trump administration's threat to step up its efforts against whistleblowers and journalists," said Ben Wizner of the American Civil Liberties Union.

Director of National Intelligence Dan Coats, who addressed the media with Sessions, issued his own tough warning to would-be leakers and described such revelations as betraying the American people.

"If you improperly disclose classified information, we will find you," he said. "We will investigate you, we will prosecute you to the fullest extent of the law."

The announcement follows a torrent of damaging revelations to the media, following six months of political intrigue and open feuding in the White House.

It comes after a leak that was unusual even by the standards of this administration - the publication by The Washington Post of the contents of private phone calls between Trump and foreign leaders.

The newspaper published the full transcripts Thursday of conversations the Republican billionaire leader held in January with Mexican President Enrique Pena Nieto and Australian Prime Minister Malcolm Turnbull.

Sessions signalled his anger over the revelations, which apparently came from inside the White House.

Disclosure of the transcripts rocked Washington, with lawmakers across the political spectrum strongly denouncing the leaks of presidential conversations with world leaders.

"Somebody needs to go to jail," Republican Senator Lindsey Graham stressed Friday on Fox News.

"You don't have the right if you work in the White House or you're a holdover from the Obama administration... to take the law in your own hands," Graham said, adding that the leaks were "hurting the presidency itself."