Russia on Saturday rejected U.S. allegations that it was responsible for cyberattacks on Ukrainian banking and government websites as baseless, the Russian embassy in the United States said on Twitter.

"We categorically reject these baseless statements of the administration and note that Russia has nothing to do with the mentioned events and in principle has never conducted and does not conduct any 'malicious' operations in cyberspace," it said.

U.S. Deputy National Security Advisor Anne Neuberger claimed on Friday that Russian military intelligence was behind the recent spate of distributed denial of service (DDoS) attacks that briefly knocked Ukrainian banking and government websites offline.

Neuberger said that Americans have data showing that infrastructure connected with Russia's military agency, generally known as the GRU, "was seen transmitting high volumes of communication to Ukraine-based IP addresses and domains."

In a simultaneous announcement on Friday, British officials said the GRU was "almost certainly involved" in the DDoS, which works by flooding targeted websites with a firehose of data.

"The attack showed a continued disregard for Ukrainian sovereignty," Britain's Foreign Commonwealth and Development Office (FCDO) said in a statement.