The US government has publicly accused Russia of conducting a hacking campaign to influence the 2016 election.
Intelligence officials said they were "confident" the Russian government was behind the series of hacking attacks and email leaks on the Democratic National Committee, and other political figures and institutions in a bid to "interfere with the US election process".
The intrusions could only have been authorised by Russia's most senior officials, the Department of Homeland Security and the Office of the Director of National Intelligence said in a statement - squarely aiming the blame at Vladimir Putin's government.
Moscow hit back with a statement saying the allegations were "nonsense", the Russian state-owned Interfax news agency reported.
"This is again some kind of nonsense. (Our) website experiences tens of thousands of attacks by hackers every day," said Kremlin spokesman Dmitry Peskov.