U.S. accusations that Russia was responsible for cyber attacks against Democratic Party organizations lack any proof and are an attempt by Washington to fan "unprecedented anti-Russian hysteria", the Foreign Ministry in Moscow said.
The U.S. government for the first time on Friday formally accused Russia of a campaign of cyber attacks against Democratic Party organizations ahead of the Nov. 8 presidential election.
Washington's relations with Moscow are also under strain over the war in Syria and Russia's actions in Ukraine.
"This whipping up of emotions regarding 'Russian hackers' is used in the U.S. election campaign, and the current U.S. administration, taking part in this fight, is not averse to using dirty tricks," Deputy Foreign Minister Sergei Ryabkov said on Saturday in comments on the ministry's website.
Late on Friday, the Kremlin called the U.S. allegations "nonsense".
"There is no proof whatsoever for such grave accusations," Ryabkov said.
"(They are) ...fabricated by those who are now serving an obvious political order in Washington, continuing to whip up unprecedented anti-Russian hysteria."
Ryabkov reiterated an offer to Washington, first made last year, to hold consultations on fighting cyber crime together.
But he also criticized John Kerry after the U.S. Secretary of State said late on Friday that Russian and Syrian actions in the Syrian civil war, including bombings of hospitals, "beg for" a war crimes investigation.
Such remarks are unacceptable and Moscow is disappointed to hear "new typically U.S. claims for being a global judge", Ryabkov said in comments to Interfax news agency published on Saturday.
Referring to a resolution on Syria proposed by France for debate at the United Security Council later on Saturday, he said: "Unfortunately, we see less and less common sense in the actions of Washington and Paris".
The draft resolution demands an end to air strikes and military flights over Aleppo. Moscow has already said this draft is unacceptable.