The Russian embassy in the United States posted a statement on Twitter on Saturday.

"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.

US Deputy National Security Advisor Anne Neuberger said 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.

"Russia likes to move in the shadows and counts on a long process of attribution," Neuberger said.

"In light of that, we're moving quickly to attribute the DDoS attacks. We believe the Russian government is responsible for widespread attacks on Ukrainian banks this week."

Neuberger said Americans had 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, British officials said the GRU was "almost certainly involved" in the DDoS, which works by flooding targeted websites with a firehose of data.

Kyiv had already blamed Moscow for the DDoS amid heightened tensions since Russia began massing troops near the border, raising fears Russia was planning to attack.

Neuberger said the attacks had "limited impact" but it was possible the Russians were laying the groundwork for more destructive ones.

Australian Associated Press