The CNN says classified documents presented last week to President Barack Obama and President-elect Donald Trump included allegations that Russian operatives claim to have compromising personal and financial information about Mr. Trump.

Quoting multiple US officials with direct knowledge of the briefings, the CNN said the allegations were presented in a two-page synopsis that was appended to a report on Russian interference in the 2016 election.

The allegations came, in part, from memos compiled by a former British intelligence operative, whose past work US intelligence officials consider credible.

The FBI is investigating the credibility and accuracy of these allegations, which are based primarily on information from Russian sources, but has not confirmed many essential details in the memos about Mr. Trump.

The classified briefings last week were presented by four of the senior-most US intelligence chiefs — Director of National Intelligence James Clapper, FBI Director James Comey, CIA Director John Brennan, and NSA Director Admiral Mike Rogers.

One reason the nation’s intelligence chiefs took the extraordinary step of including the synopsis in the briefing documents was to make the President-elect aware that such allegations involving him are circulating among intelligence agencies, senior members of Congress and other government officials in Washington, multiple sources tell CNN.

These senior intelligence officials also included the synopsis to demonstrate that Russia had compiled information potentially harmful to both political parties, but only released information damaging to Hillary Clinton and Democrats. This synopsis was not an official part of the report from the intelligence community case about Russian hacks, but some officials said it augmented the evidence that Moscow intended to harm Clinton’s candidacy and help Trump’s, several officials with knowledge of the briefings tell CNN.

The two-page synopsis also included allegations that there was a continuing exchange of information during the campaign between Trump surrogates and intermediaries for the Russian government, according to two national security officials.

Sources tell CNN that these same allegations about communications between the Trump campaign and the Russians, mentioned in classified briefings for congressional leaders last year, prompted then-Senate Democratic Leader Harry Reid to send a letter to FBI Director Comey in October, in which he wrote, “It has become clear that you possess explosive information about close ties and coordination between Donald Trump, his top advisors, and the Russian government — a foreign interest openly hostile to the United States.”