The U.S. Department of Homeland Security and the Office of the Director of National Intelligence have accused Russia of deliberately hacking e-mail servers of U.S. individuals and political organizations to interfere with the election campaign ongoing in the country.

"The U.S. Intelligence Community (USIC) is confident that the Russian government directed the recent compromises of e-mails from U.S. persons and institutions, including from U.S. political organizations," the U.S. Department of Homeland Security and the Office of the Director of National Intelligence said in a joint statement.

"These thefts and disclosures are intended to interfere with the U.S. election process," the document says.

"Such activity is not new to Moscow - the Russians have used similar tactics and techniques across Europe and Eurasia, for example, to influence public opinion there," it says.

"We believe, based on the scope and sensitivity of these efforts, that only Russia's senior-most officials could have authorized these activities," the statement says.