Is Trump at risk of being blackmailed by Russia?

US intelligence have told President-elect Donald Trump that Russian operatives claim to have "compromising" personal and financial information about him, CNN reported.

Citing "multiple" unnamed US officials with direct knowledge of the meeting last week, CNN said the intelligence chiefs presented a two-page synopsis on the potential embarrassment for the incoming president.

It came along with a classified briefing on Friday on alleged Russian interference in the presidential election, which President Barack Obama was briefed on.

CNN gave no details of what the so-called compromising information is, but said knowledge of its existence in Russian hands originally came from 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.

The Federal Bureau of Investigation had been given the information in August, more than two months before the 8 November election, according to CNN.

"What has changed since then is that US intelligence agencies have now checked out the former British intelligence operative and his vast network throughout Europe and find him and his sources to be credible enough to include some of the information in the presentations" to Trump, CNN said.

The existence of the information on Trump in Russian hands has been rumored since before the election.

The rumours gained support with a letter to the FBI from the then Democratic leader in the Senate Harry Reid a 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 - a foreign interest openly hostile to the United States, which Trump praises at every opportunity. The public has a right to know this information."

In the Friday briefing Trump was also told by the intelligence officials - the heads of the Directorate of National Intelligence, the CIA, the FBI and the NSA - of allegations that supporters of his White House campaign had a "continuing exchange of information" with intermediaries for the Russian government during the election.

Asked about this in a Senate hearing Tuesday, Comey refused to confirm or deny that his agency was investigating such links.

US intelligence has concluded that Russian President Vladimir Putin ordered an operation to meddle in the US election to hurt the campaign of Democratic candidate Hillary Clinton with embarrassing hacked emails, and then to boost Trump when they thought he had a chance to win.

Trump has repeatedly dismissed the conclusion that Moscow influenced the election while expressing the need to smooth over bilateral relations deeply strained during the Obama presidency.