US President-elect Donald Trump rejected as "ridiculous" reported US intelligence findings that Russia intervened in the presidential election on his behalf through targeted hacking, saying he did not believe it, according to an interview on Fox News Sunday.

The Republican president-elect's comments casting doubt on reported US intelligence findings pits him against some leading foreign policy voices in the US Senate from his own party who on Sunday expressed alarm about election meddling by Moscow.

"I think it's ridiculous. I think it's just another excuse. I don't believe it," Trump said in the interview, which was taped on Saturday.

He blamed Democrats for putting out the media reports and said he did not believe they came from the Central Intelligence Agency.

Trump's dismissal was perhaps aimed at squashing doubts about whether he won the November 8 election fairly. However, his comments could also portend conflicts between the new president and the intelligence agencies he will command and feed criticism that his administration will be soft on Russia.

The Republican real estate magnate was expected to appoint as secretary of state Exxon Mobile Corp Chief Executive Rex Tillerson, who has close ties with Moscow and has spoken out against US sanctions on Russia.

US intelligence agencies have told Congress and the administration of President Barack Obama that Russia has grown increasingly aggressive in Syria and Ukraine and has stepped up activities in cyberspace including meddling, sometimes covertly, in European and US elections.

A senior US intelligence official told Reuters intelligence agencies have concluded with "high confidence" that not only did their Russian counterparts direct the hacking of Democratic Party organisations and leaders, but they did so to undermine Democratic candidate Hillary Clinton.

Photo: Reuters

The Republican president-elect questioned whether the Central Intelligence Agency was behind the reports that indicated Moscow wanted him in the White House. "I think the Democrats are putting it out," he said in the interview.

Two leading Republican voices on foreign policy in the US Senate, John McCain and Lindsey Graham, joined two Democratic senators on Sunday in expressing concern over possible Russian interference in a U.S. presidential election.

"For years, foreign adversaries have directed cyber attacks at America's physical, economic, and military infrastructure, while stealing our intellectual property. Now our democratic institutions have been targeted," the senators, including Democrats Chuck Schumer and Jack Reed, said in a statement.

"Recent reports of Russian interference in our election should alarm every American."

"This cannot become a partisan issue. The stakes are too high for our country," the senators said in a statement.

Reince Priebus, the Republican Party leader Trump picked to be his chief of staff in the White House, attacked the news reports for relying on unidentified sources and denied a New York Times report that the Republican National Committee was hacked. He was speaking on NBC's Meet the Press.

Russian officials have denied all accusations of interference in the US election.