Russian hackers could attempt to fabricate signs of vote rigging in an attempt to cast doubts over the result of the US presidential election, officials told the Washington Post.

Intelligence officials have accused Russia of attempting to interfere with the results of the election for months, by hacking the email servers of the Democrat Party and leaking confidential emails to the WikiLeaks website.

Officials believe that the interference attempts are likely to extend to the day of the election on 8 November and beyond, with Russia expected to attempt further hacks or fabricate information calling into doubt the integrity of the election process.

"I think it's correct to say the Russians don't think they can dictate the outcome," Rep Adam B Schiff, the top Democrat on the House Intelligence Committee told the newspaper. But as votes are being tallied on Tuesday Russian intelligence services are likely to be "looking through their troves of hacked documents and seeing what they can release."

A Department of Homeland Security official told the newspaper that there was evidence of Russian "scanning" of state-run databases and computer voting systems.

Schiff and other officials said Russia could dump doctored documents designed to indicate vote rigging.

The claims echo those of the most senior Democrat in the Senate, Harry Reid, who in August called on the FBI to investigate evidence that Russia was attempting to manipulate voting results.

On Thursday, the FBI and US intelligence agencies announced they were investigating faked documents aimed at discrediting Clinton's campaign, including a fake letter from Tom Carper, a Democrat on the Senate Homeland Security Committee, in which he pledges to Clinton: "We will not let you lose this election." The documents are believed to be part of the Russian disinformation campaign.

Russia has denied any involvement in the hacks, and President Vladimir Putin dismissed claims that Russia was trying to interfere with the result of the election.

Claims of Russian involvement in the hacks is backed by several US intelligence agencies and cyber security experts.

Republican presidential candidate Donald Trump has been accused of being a "puppet" of Putin by Democrat challenger Hillary Clinton. Trump has denied that there is evidence Russia is behind the hacks.