US President-elect Donald Trump tonight dismissed as "nonsense" the media claims that Russia has compromising information on him, saying the allegations may have been leaked by US intelligence agencies and it would be a "tremendous blot" on their record if they did that.

"I think it's a disgrace that information would be let out. I saw the information, I read the information outside of that meeting," Trump told reporters in his first formal press conference in six months.

Referring to a dossier with allegations that Russia has compromising material on him, the President-elect said, "It's all fake news. It's phony stuff. It didn't happen."

He, however, acknowledged that Russia and some other countries were behind the hacking of Democratic Party computers.

"As far as hacking, I think it was Russia, but I also think we've been hacked by other countries, other people," he said addressing the crowded press conference nine days from his inauguration as the 45th president of the US.

"The DNC was totally open to be hacked. They did a very poor job," he said, adding that attempts to hack the Republican National Committee were unsuccessful and "they were unable to break through."

A visibly composed Trump said his team is going to put "some of the greatest computer minds" together and put up a defence against hacking by foreign entities.

The press conference came amid media reports that chiefs of American intelligence agencies had last week presented President Barack Obama and Trump with a summary of unsubstantiated reports that Russia had collected compromising and salacious personal information about Trump.

"Sick people, group of opponents have put them together. It shouldn't have entered paper, its an absolute disgrace," he said, referring to the allegations.

Alluding to Moscow’s response on the leak of intelligence information, Trump said Putin and Russia said this was fake news.

"I respected the fact that he said that. If they had broken into RNC they would have released it," he said.

If Putin likes Donald Trump, it is an asset not a liability. I hope I do get along with Putin, there’s good chance I won't," he said.

Trump said his administration will come out with a major report on hacking within 90 days.