In Ukraine, the defence ministry said its web portal had been hit by an unprecedented cyber attack that was into its second day.
The Russian defence ministry published video that it said showed tanks, infantry fighting vehicles and self-propelled artillery units leaving the Crimean peninsula, which Moscow seized from Ukraine in 2014.
Their deployment was part of a huge build-up of Russian forces to the north, east and south of Ukraine since November that had prompted London and Washington to warn in recent days that a Russian invasion looked imminent.
Russia mocked those warnings as hysterical war propaganda when it announced on Tuesday that some units were starting to return to base after completing exercises.
Military analysts say a key indicator of a significant pullback will be whether units from Russia's far east, which are taking part in huge exercises in Belarus this week, return to their bases thousands of kilometres away.
US President Joe Biden said on Tuesday that more than 150,000 Russian troops were still amassed near Ukraine's borders. He said Washington had not yet verified any pullout.
"Our analysts indicate that they remain very much in a threatening position," he said.
British Defence Secretary Ben Wallace told Times Radio on Wednesday: "We haven't seen any evidence at the moment of that withdrawal."
Speaking separately to the BBC, he said: "Physical observations that we see show the opposite of some of the recent rhetoric coming out the Kremlin."
In Ukraine, the defence ministry said hackers were still bombarding its website and had succeeded in finding vulnerabilities in the programming code.
Although Kyiv did not name who was behind the incident, a statement suggested it was pointing the finger at Russia.
"It is not ruled out that the aggressor used tactics of dirty little tricks because its aggressive plans are not working out on a large scale," said the Ukrainian Centre for Strategic Communications and Information Security, which is part of the culture ministry.
Russia's Federal Security Service did not immediately reply to a request for comment from Reuters.
"If Russia attacks the United States or our allies through asymmetric means like disruptive cyber attacks against our companies or critical infrastructure, we're prepared to respond," Biden said in televised remarks from the White House on Tuesday.
Russia has always denied planning to invade Ukraine but has been pressing for a set of security guarantees from the West including a promise that its neighbour Ukraine will never join NATO.
The United States and its allies have rejected that, but say they are willing to talk about arms control and confidence-building measures.
Putin said after meeting German Chancellor Olaf Scholz on Tuesday that the West was ignoring Russia's main demands but Moscow was ready to continue dialogue on security issues.
European Union Council head Charles Michel urged Russia on Wednesday to take tangible steps to de-escalate.
"The choice today is a choice between war and tragic sacrifices that would go along with that war or the courage of a political engagement, the courage of a diplomatic negotiation", he said.
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