Russia's claims that Ukraine is delaying exchange of soldiers' bodies are untrue, Ukrainian officials said on Saturday, urging Moscow to stop "playing dirty games" and return to constructive work. Kremlin aide Vladimir Medinsky said on Saturday that Ukraine had unexpectedly postponed exchanging prisoners of war and accepting the bodies of killed soldiers for an indefinite period.

The attacks come days after Trump says Putin had "very strongly" promised response to Ukraine "Spider web" attack.

The Kremlin said on Friday the Ukraine war was "existential" for Russia, after it launched a wave of retaliatory drone and missile strikes that killed at least four people.

Russia struck Ukraine with a thunderous aerial bombardment overnight, further dampening hopes that the warring sides could reach a peace deal anytime soon.

Since last sitting down with Ukraine to talk peace, Russia has launched four of its five largest drone attacks against the country, killed more than 340 of its civilians and continued to peddle its false narrative about the unprovoked war it has been waging for more than a decade.

It restated Moscow's demands that Ukraine become a neutral country - ruling out membership of NATO - and that it protect the rights of Russian speakers, make Russian an official language and enact a legal ban on glorification of Nazism. Ukraine rejects the Nazi charge as absurd and denies discriminating against Russian speakers.