Donald Trump finally concedes Russia may have been behind election hacking

But refutes intelligence reports that Moscow acted to help him win the presidential race

US President-elect Donald Trump for the first time has acknowledged Russian involvement in the Democratic National Committee (DNC) server hack but refuted intelligence reports that Moscow acted to help him win the presidential race.

"I think it was Russia," the CNN quoted Trump as saying at a news conference in New York on Wednesday.

He added that Russia is not the only nation that hacks US targets and accused Democrats of not having sufficient cyber-security programs.

The news conference opened with his spokesman, Sean Spicer, slamming a "political witch hunt" following reports that Russian operatives claim to have compromising personal and financial information about Trump.

Vice President-elect Mike Pence also criticized the media before introducing Trump, who kept up his criticism of US intelligence.

On the issue of releasing his tax returns publicly, the President-elect reiterated that he doesn't plan to release them, saying they are under audit and don't include relevant information.

The news conference followed media reports that that classified documents presented last week to President Barack Obama and Trump included the allegations about Russia. The allegations were presented in a two-page synopsis that was appended to a report on Russian interference in the 2016 election and drew 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.

Trump denounced news reports that US officials had obtained an unsubstantiated dossier of potentially compromising personal information Russia has allegedly gathered about him, citing denials from the Kremlin that it has any such intelligence.