Trump slams reports of Russian blackmail dossier as 'fake news'

US spy chiefs have informed Donald Trump that Russian operatives claim to possess deeply compromising personal and financial information about him, US media reported on Tuesday on the eve of the president-elect's first press conference.

Trump denounced in block capitals what he called a "political witch hunt", after CNN reported that intelligence officials briefing him last week on allegations of Russian meddling in the US election had also given him a synopsis of the explosive and unverified claims. Russia later denied it had anything on the president-elect.

Intelligence chiefs last week presented America's incoming 45th president, as well as current President Barack Obama, with a two-page synopsis on the potential embarrassment, according to CNN and The New York Times, who cited multiple unnamed US officials with direct knowledge of the meeting.

Obama delivered his farewell address on Tuesday evening as the bombshell report was reverberating in political and diplomatic circles with just 10 days to go until Trump's inauguration.

The outgoing US leader had little to add publicly to the bombshell revelations.

"You know I hadn't seen the reports, we were on the plane together, and I hadn't read the news since then and as a matter of principle and national security I don't comment on classified information," the president said in an interview with NBC News late on Tuesday.

He added, however, that he hopes Congress and the Trump administration will continue to work toward finding answers about who is responsible for hacking scandals that have roiled American politics in recent months. 

CNN gave no details of the allegations, but US media outlet Buzzfeed published, without corroborating its contents, a 35-page dossier of memos on which the synopsis is based, which had been circulating in Washington for months.

The memos describe sex videos involving prostitutes filmed during a 2013 visit by Trump to a luxury Moscow hotel, supposedly as a potential means for blackmail.

They also suggest Russian officials proposed lucrative deals in order to win influence over the Republican real estate magnate.

It stated that Trump Organisation lawyer, Michael Cohen, had met Russian officials in Prague during the presidential election to prevent any of the information coming out. 

Cohen posted on Twitter that he had never been to Prague, and uploaded a picture of the front of his passport as proof - to much ridicule.

The dossier was originally compiled by a former British MI6 intelligence operative hired by other US presidential contenders to do political "opposition research" on Trump in the middle of last year, according to CNN.

An anonymous US official told Reuters that the Federal Bureau of Investigation and other US agencies are continuing to investigate the credibility and accuracy of the claims.

Questions over claim

The official said that investigators so far have been unable to confirm the material about Trump's financial and personal entanglements with Russian businessmen and others whom US intelligence analysts have concluded are Russian intelligence officers or working on behalf of Russian intelligence.

Some material in the reports produced by the former British intelligence officer has proved to be erroneous, the official said.

The FBI has not yet commented on the investigation.

Trump was reportedly informed of the existence of the dossier - and its salacious details - last Friday when he received a briefing from US intelligence chiefs on alleged Russian interference in the presidential election.

The classified two-page synopsis also included allegations that there was a regular flow of information during the campaign between Trump surrogates and Russian government intermediaries.

"Nothing's been confirmed," Trump senior aide Kellyanne Conway told NBC about the material. "They're all unnamed, unspoken sources."

Democrats were left stunned by the developments.

"If these allegations are true, allegations of coordination between Trump campaign officials and Russian intelligence officials, and allegations that the Russians have compromised President-elect Trump's independence, that would be truly shocking," Democratic Senator Chris Coons said on CNN.

House Democrat Jared Polis took it further.

"If the reports of Trump being compromised are not true they must be refuted," Polis posted on Twitter. "If true he should not be president."

The FBI was provided with the information in August, more than two months before the 8 November election.

Since then US spy agencies have checked out the former British intelligence operative and his network, and found him credible enough to include some of the information in the presentation to Trump, according to CNN.

The existence of compromising and salacious information on Trump in Russian hands had been rumoured since before the election.

The rumours gained momentum when then Senate Democratic leader Harry Reid wrote to FBI director James Comey one week before the vote.

"It has become clear that you possess explosive information about close ties and coordination between Donald Trump, his top advisors, and the Russian government," Reid wrote in his letter.

"The public has a right to know this information."

Comey was one of four top officials who briefed Trump on Friday, along with the heads of the Directorate of National Intelligence, the Central Intelligence Agency and the National Security Agency. 

Asked in a Senate hearing on Tuesday about the allegations of sustained contacts between Russia and the Trump team, Comey refused to confirm or deny his agency was investigating such links.

US intelligence has already made the virtually unprecedented accusation that Russian President Vladimir Putin sought to tip the electoral scales in Trump's favour by ordering a hack of Democratic Party emails.

Trump has repeatedly dismissed the conclusion that Moscow influenced the election, while calling for a push to mend bilateral relations deeply strained during the Obama presidency.

At the weekend he condemned as "stupid" anyone opposing better relations with Moscow.