Several people were killed in overnight strikes that came after both Moscow and Kyiv announced uniliteral ceasefires over different dates this week.

Moscow has announced a ceasefire during public World War II celebrations over May 9, while Kyiv has said it will halt fire over May 6.

"It is utter cynicism to ask for a ceasefire in order to hold propaganda celebrations while carrying out such missile and drone strikes every single day leading up to it," Zelensky said in a statement in response to the attacks.

"Russia could cease fire at any moment, and this would stop the war and our responses," he added.

The Russian May 9 parade is typically a bombastic display of military strength, which since 2022 has sought to link Soviet victory over Nazi Germany with the invasion of Ukraine.

But the Kremlin ordered a scaled-back version this year -- with no military hardware to be on display -- over the fear it could be targeted by Ukraine.

Moscow also cut mobile internet throughout the Russian capital on Tuesday morning ahead of the parade, with operators reporting restrictions would last until Saturday.

Kyiv has intensified its retaliatory long-range strikes in recent weeks, hitting a spate of Russian oil facilities and a luxury high-rise building in Moscow.

It calls the strikes fair retaliation for Russia's nightly bombarding of its cities with drones and missiles.

- 'Vile' -

Overnight, a Russian strike killed four people in the central Poltava region -- employees of state energy firm Naftogaz and first responders, triggering outrage in Kyiv.

"Two of the killed were first responders, killed in a vile double-tap strike targeting those who arrived to help people at the scene of the attack. Only a terrorist state like Russia employs inhuman and criminal tactics like these," Ukraine's Foreign Minister Andriy Sybiga said.

The state emergency service said Russia fired four missiles at the site after an earlier drone hit, publishing video of a fireball erupting at the facility.

One person was also killed in the northeastern Kharkiv region as Russia fired 11 ballistic missiles and 164 drones across the country, according to authorities.

Later on Tuesday a Ukrainian drone slammed into an apartment block in the Russian city of Cheboksary, some 1,000 kilometres (620 miles) from the front line in eastern Ukraine.

Russia's Investigative Committee said there were "dead and wounded", without providing numbers, after unverified videos on social media showed a fireball in the side of a multi-storey apartment block.

The Russian defence ministry said it had targeted Ukraine's defence sector and energy sites in response to "attacks on civilian targets in Russia".

It said Russia had downed more than 300 Ukrainian drones between late Monday and early Tuesday, with several airports across the country temporarily halting flights throughout the morning.

Short-term ceasefires are not infrequent, with the two sides having suspended long-range attacks over Orthodox Easter last month.

There is no sign that the four-year war is close to being resolved at the negotiating table.

Ukrainian political analyst Volodymyr Fesenko told AFP the counter-truces were a "tactical struggle" between the two sides on the political front.

"If Russia does not abide by our ceasefire, accordingly, we have every right not to abide by their ceasefire. This nullifies Putin's initiative," he told AFP.

Moscow is demanding Kyiv fully withdraw its troops from the eastern Donbas area and renounce Western military support -- ultimatums seen as tantamount to capitulation in Kyiv, which has rejected them.

On the battlefield, Russia's progress has stalled -- with its army losing more territory than it captured in April for the first time since summer 2023, according to an AFP analysis of data from the Institute for the Study of War (ISW).

The war has spiralled into the bloodiest conflict in Europe since World War II, claiming the lives of hundreds of thousands of people and displacing millions.