Special Counsel Robert Mueller's office took the rare step of disputing a news report on his Russia investigation, saying a BuzzFeed article alleging that US President Donald Trump directed his former lawyer to lie to Congress is "not accurate".

The rebuke of the report late on Friday came as Trump's allies strongly pushed back against the claim, which said that the president ordered Michael Cohen to lie about a Moscow skyscraper project they pursued during the 2016 election.

"BuzzFeed's description of specific statements to the Special Counsel's Office, and characterization of documents and testimony obtained by this office, regarding Michael Cohen's Congressional testimony are not accurate," spokesperson Peter Carr said in a statement.

"I appreciate the special counsel coming out with a statement last night. I think it was very appropriate that they did so," Trump told reporters at the White House. "I think that the BuzzFeed piece was a disgrace to our country. It was a disgrace to journalism."

In a tweet posted after Mueller's statement, BuzzFeed editor-in-chief Ben Smith said the news outlet stood by the original report.

"In response to the statement tonight from the Special Counsel's spokesman: We stand by our reporting and the sources who informed it, and we urge the Special Counsel to make clear what he's disputing," he wrote.

In response to the statement tonight from the Special Counsel's spokesman: We stand by our reporting and the sources who informed it, and we urge the Special Counsel to make clear what he's disputing. — Ben Smith (@BuzzFeedBen) January 19, 2019

Ongoing probe

Mueller's investigation into Russian interference in the 2016 vote and possible collusion between Trump's campaign and Moscow is the subject of frequent articles and even more frequent speculation.

But it is extremely rare, if not unprecedented, for his office to issue such a statement.

The statement was a cause for celebration for the president, who retweeted numerous supporters slamming BuzzFeed and later wrote it was "a very sad day for journalism, but a great day for our Country!"

Later adding: "Fake News is truly the ENEMY OF THE PEOPLE!"

Fake News is truly the ENEMY OF THE PEOPLE! — Donald J. Trump (@realDonaldTrump) January 19, 2019

Trump's lawyer Rudy Giuliani had earlier called the allegation in the BuzzFeed report "categorically false" in a comment sent to several White House reporters, while Deputy White House Spokesman Hogan Gidley labelled the report "ridiculous". He said Cohen is someone "who now quite frankly has been proven to be a liar".

Democrats in Congress had pledged to investigate the report to see if the president had committed an impeachable felony.

"These allegations may prove unfounded, but, if true, they would constitute both the subornation of perjury as well as obstruction of justice," said Adam Schiff, the chairman of the House Intelligence Committee.

The BuzzFeed article was based on interviews with two anonymous "federal law enforcement officials" who are familiar with Cohen's testimony to the investigation led by Mueller.

No other media have confirmed BuzzFeed's reporting.

Cohen was the president's right-hand man for years at the Trump Organization, the umbrella company, often relied upon to quietly fix difficult problems and negotiate deals for the real estate mogul.

But he has turned on his former boss after he was charged with giving hush money to women alleging affairs with Trump ahead of the 2016 election, payments that violated campaign finance laws.

Cohen, who has been sentenced to three years in jail, said Trump ordered him to make the payments, and now says he regrets his work for the president.