Russia's missile and drone attacks on power stations and other infrastructure in Ukraine are "acts of pure terror" that amount to war crimes, European Commission President Ursula von der Leyen said on Wednesday.

"Yesterday we saw again Russia's targeted attacks against civilian infrastructure. This is marking another chapter in an already very cruel war. The international order is very clear. These are war crimes," von der Leyen said in a speech to lawmakers in the European Parliament.

"Targeted attacks on civilian infrastructure with the clear aim to cut off men, women, children of water, electricity and heating with the winter coming, these are acts of pure terror and we have to call it as such."

Russia has destroyed almost a third of Ukraine's power stations in the past week, President Volodymyr Zelenskyy said on Tuesday.

Missiles struck power stations in the capital Kyiv where they killed three people, and in Kharkiv in the east, Dnipro and Kryvyi Rih in the south, and Zhytomyr in the west, causing blackouts and knocking out water supplies. One man was killed in his flat that was destroyed in Mykolaiv in the south.

"The situation is critical now across the country ... The whole country needs to prepare for electricity, water and heating outages," Kyrylo Tymoshenko, deputy head of the Ukrainian president's office, told Ukrainian television.

Russia has openly acknowledged targeting Ukraine's energy infrastructure with waves of missile and drone strikes since the start of last week, in what President Vladimir Putin said was legitimate retaliation for a blast on a bridge.

Kyiv and the West say intentionally attacking civilian infrastructure is a war crime, and the attacks, aimed at leaving Ukrainians with no heat and power as winter arrives, are Putin's latest tactic to escalate a war his forces are losing.

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Zelenskyy said Russia was continuing to try to terrorise and kill Ukrainian civilians.

"Since October 10, 30 percent of Ukraine's power stations have been destroyed, causing massive blackouts across the country," he wrote on Twitter.

Zelenskyy reiterated his refusal to negotiate with Putin who he says heads a "terrorist state."

There was no immediate word on how many people were killed in Tuesday's strikes overall. A day earlier, Russia sent swarms of drones to attack infrastructure in Kyiv and other cities, killing at least five people.

The Russian defense ministry repeated earlier statements that it was carrying out attacks using high precision weapons on what it described as military targets and energy infrastructure across Ukraine.

Ukraine accuses Russia of using Iran-made Shahed-136 'kamikaze drones', which fly to their target and detonate. Iran denies supplying them and on Tuesday the Kremlin also denied using them.