HR McMaster, US President Donald Trumps national security adviser, said at the Munich Security Conference that the federal indictments showed the US was becoming "more and more adept at tracing the origins of this espionage and subversion."
"As you can see with the FBI indictment, the evidence is now really incontrovertible and available in the public domain," McMaster told a Russian delegate to the conference.
Just minutes before, Russian Foreign Minister Sergey Lavrov had dismissed the indictments as "just blabber," according to remarks through an interpreter.
"You can publish anything, and we see those indictments multiplying, the statements multiplying."
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The two men addressed the conference of top world leaders, defense officials and diplomats, giving more general back-to-back opening remarks.
But both were immediately hit with blunt questions about the US indictment and the broader issue of cyberattacks.
In Russia, news of the indictments was met with more scorn.
"There are no official claims, there are no proofs for this. Thats why they are just childrens statements," Andrei Kutskikh, the presidential envoy for international information security, told Russian state news agency RIA Novosti.