Classified documents that the heads of four US intelligence agencies presented last week to President-elect Donald Trump included claims that Russian intelligence operatives have compromising information of a sexual nature about him, two US officials said last night.
They told Reuters the claims, which one called "still unsubstantiated," were contained in a two-page memo appended to a report on Russian interference in the 2016 election that US intelligence officials presented to Mr Trump and President Barack Obama last week.
Mr Trump responded yesterday evening in a tweet calling the reports: "FAKE NEWS - A TOTAL POLITICAL WITCH HUNT!"
The Trump transition team did not immediately respond to a request for comment.
Mr Trump added another response in a tweet today saying "intelligence agencies should never have allowed this fake news to 'leak' into the public".
Intelligence agencies should never have allowed this fake news to "leak" into the public. One last shot at me.Are we living in Nazi Germany?— Donald J. Trump (@realDonaldTrump) January 11, 2017
I win an election easily, a great "movement" is verified, and crooked opponents try to belittle our victory with FAKE NEWS. A sorry state!— Donald J. Trump (@realDonaldTrump) January 11, 2017
One of the officials, both of whom requested anonymity to discuss classified matters, said the Federal Bureau of Investigation and other US agencies are continuing to investigate the credibility and accuracy of the claims.
They are included in opposition research reports made available last year to Democrats and US officials by a former British intelligence official, most of whose past work US officials consider credible.
The official said investigators so far have been unable to confirm the material about Mr 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.
Russia has never tried to use leverage over me. I HAVE NOTHING TO DO WITH RUSSIA - NO DEALS, NO LOANS, NO NOTHING!— Donald J. Trump (@realDonaldTrump) January 11, 2017
Some material in the reports produced by the former British intelligence officer has proved to be erroneous, the official said.
The FBI declined to comment.
A Kremlin spokesman this morning said Russia does not have compromising information on Mr Trump.
He dismissed the "fake" claims as being aimed at damaging Russia's ties with the US.
The charges that Russia attempted to compromise Mr Trump were presented to the FBI and other US government officials last summer and have been circulating for months.
The FBI initially took the material seriously, said the sources, who spoke on condition of anonymity because of the sensitivity of the issue, which was first reported by CNN.
However, the FBI failed to act on the material, and the former British intelligence officer broke off contact about three weeks before the November election, they said.
The warning of information about Russia's compromising claims follows growing US intelligence and law enforcement concerns about what Director of National Intelligence James Clapper has called "multifaceted" Russian influence and espionage operations in Europe and the United States.
In addition to hacking computer networks and spreading propaganda and fake news, it includes efforts to cultivate business and political leaders and find compromising personal, financial and other information on persons of interest, US intelligence officials said.
The classified briefings last week were presented to Mr Obama and Mr Trump by Mr Clapper, FBI Director James Comey, Central Intelligence Agency Director John Brennan and National Security Agency Director Mike Rogers.
US intelligence chiefs included a classified summary of the material to make Mr Trump aware that it is circulating among intelligence agencies, senior members of Congress, government officials and others, one of the officials said.
An unclassified intelligence report released on Friday concluded that Russian President Vladimir Putin ordered an effort to help Mr Trump's electoral chances by discrediting Democrat Hillary Clinton in the 2016 presidential campaign.
The report said US intelligence agencies have concluded that as part of the effort Russia's military intelligence agency, the GRU, used intermediaries such as WikiLeaks and others to release emails it hacked from the Democratic National Committee and top Democrats.