US President-elect Donald Trump says allegations Russia has compromising material on him are "fake news, phoney stuff", put together by "sick people".
He was replying to allegations carried in some US media that his election team colluded with Russia and there were salacious videos of his private life.
In his first briefing as president-elect, he also said for the first time Russia had been behind hacking attacks.
He also confirmed handing total control of his businesses to his two sons.
The press conference was scheduled for Trump to give details about his business affairs but was dominated by the allegations of the compromising material.
Trump said the claims "should never have been written and should never have been released".
"It's all fake news, it's phoney stuff, it didn't happen," he said, saying that "sick people" had "put that crap together... it's an absolute disgrace".
He thanked the news organisations that chose not to run with the claims, which have been circulating for months.
Intelligence agencies reportedly considered them sufficiently relevant to brief both Trump and President Barack Obama last week.
Trump would not confirm he had been briefed but he then said there had been a "lot of people in the room" and that it would be a "tremendous blot" on the reputation of intelligence agencies if they had been responsible for leaking the details.
"That's something that Nazi Germany would have done," he said.
A 35-page dossier of allegations had been published in full on Buzzfeed and reported by CNN.
Trump called Buzzfeed a "failing pile of garbage" and accused CNN of "going out of their way to build it up".
The allegations claim Russia has damaging information about the president-elect's business interests, and salacious video evidence of his private life, including claims of using prostitutes at the Ritz-Carlton hotel in Moscow.
Denying any such claims, Trump said that as a high-profile person he was extremely cautious about all that he did when travelling abroad.
Russia has also strongly denied the allegations.
Dmitry Peskov, President Vladimir Putin's spokesman, said they were "pulp fiction" and a "clear attempt to damage relations".
Trump said he "respected" Putin for putting out a statement.
Trump was also asked about the hacking scandal that dominated the US election campaign, with US spy agencies concluding Russia was behind the hacking of Democratic Party emails.
Trump said for the first time "I think it was Russia", but added that "we get hacked by other people".
Later in the briefing, he suggested the outcome was justified, saying "look at the things that we learned... Hillary Clinton got the questions to the debate and didn't report it".
He added: "If Putin likes Donald Trump, I consider that an asset, not a liability."
Trump did not answer directly when asked whether his team had communicated with Russia during the election campaign, but he did say that any hacking by Putin must stop. "He shouldn't be doing it. He won't be doing it."