US President Donald Trump said - on Tuesday - that he had declassified all documents related to federal investigations into Russian interference in the 2016 US presidential elections.

He added that he also allowed the declassification of all documents related to the investigations into the use of former Secretary of State Hillary Clinton of her (unsafe) mail in government correspondence.

"I have authorized the complete declassification of all documents relating to the greatest political crime in American history, the hoax of Russia, and likewise, the email scandal of Hillary Clinton. Do not edit!" Trump wrote in a tweet.

This step comes after the US Department of Homeland Security escalated its warnings on Tuesday of external threats to the security of the upcoming presidential elections, despite the absence of evidence for this.

In a 26-page report titled "Assessing Internal Threats," the Department of Homeland Security argued that Russia was likely to be the main likely covert influence factor and the party that was broadcasting false and misleading information inside the country.

The ministry claimed that it concluded in its assessment that Moscow's main goal is to strengthen its global position and influence, by weakening the United States - internally and externally - through efforts to sow discord and dispersion, form public sentiment, and undermine confidence in Western democratic institutions and processes.

The report also stated that Russia is using divisive measures to disrupt the electoral process, including discrediting Biden, the former Vice President and what it sees as an opposing institution, as part of a greater effort to foment division and destabilize America.

Earlier, Russian presidential spokesman Dmitry Peskov described reports of Moscow's interference in the US elections as "nonsense," in response to an article in which the New York Times claimed that Russia would try to help President Trump win a second term in the 2020 elections.