The former US president Donald Trump's administration "secretly" obtained the phone records of three Washington Post journalists, the newspaper reported on Friday. All three journalists, Ellen Nakashima, Greg Miller and Adam Entous, had reported on allegations of Russian meddling in the 2016 presidential election Among them, Entous is a former Post reporter.

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The US Justice Department sent letters to the three reporters - saying that it had received work, cell or home phone records "for the period from April 15, 2017, to July 31, 2017," according to the Post.

"We are deeply troubled by this use of government power to seek access to the communications of journalists," said the Post's acting executive editor Cameron Barr.

"The Department of Justice should immediately make clear its reasons for this intrusion into the activities of reporters doing their jobs, an activity protected under the First Amendment," he added.

The report has sparked concerns over freedom of speech, with American Civil Liberties Union (ACLU) saying that the Justice Department had been "spying" on the journalists "at the whims of an administration."

"This should never have happened," it tweeted.

"When the government spies on journalists and their sources, it jeopardizes freedom of the press," the ACLU added.

The Justice Department said it had followed "established procedures" with the requests, the Post reported, citing a department spokesman.

The letters did not specify why the records were seized.

But, near the end of that period, the three wrote a story about US intelligence which suggested that Jeff Sessions, who later became attorney general under Donald Trump, had discussed the Trump campaign with the Russian ambassador, reported AFP.

They also wrote a story on the Obama administration's efforts to counter Russian interference in the 2016 election.

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US intelligence agencies have concluded Russia hacked into the computer servers of the Democratic National Committee (DNC) during Trump's campaign against Democratic rival Hillary Clinton.

However, Trump has played down Russia's involvement in the DNC leak.