President Donald Trump publicly rejected Russia's accusations of a Ukrainian drone attack on Vladimir Putin's residence, having previously appeared to back the claims.

"I don't believe that strike happened," Trump said in response to a reporter's question aboard Air Force One, noting how "nobody knew at that moment" whether the report was true.

Last week, Russia's defense ministry published a video of a downed drone it said Ukraine had launched at Putin's home in the Novgorod region, adding that the property was not damaged and the leader was elsewhere at the time.

The accusation came at a crunch moment, with diplomacy aimed at brokering an end to the nearly four-year war picking up pace, and as Ukrainian President Volodymyr Zelensky traveled to Florida to meet with Trump.

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Kyiv and its Western allies have insisted allegations of an attack were meant to sabotage negotiations, but Trump initially seemed to accept the Kremlin's account.

On Sunday, he merely said that "something" had happened near Putin's residence, but that after reviewing the evidence, US officials did not believe it had been targeted by Ukraine.

Zelensky has meanwhile blamed Russia for carrying the war "into the New Year" with a series of deadly bombardments.

A countrywide air raid siren was issued early Monday morning in Ukraine, and attacks on the Kyiv region killed at least two people, authorities reported.

Russia made bigger advances on the battlefield last year than any other since it launched its invasion in 2022, according to an AFP analysis of data from the Institute for the Study of War.

European leaders are expected to convene in France on Tuesday for further talks on a US-backed plan to end Europe's deadliest conflict since World War II, which Zelensky says is "90% ready."