KYIV: The reconnection of the nation's four nuclear power reactors helped Ukrainian authorities gradually restore power on Friday, but millions of people were left without power following the deadliest Russian airstrikes of the war.

Ukrainian President Volodymyr Zelenskiy urged with people to conserve electricity. In an evening video message, he clarified that just because there is energy doesn't imply you may use many potent electrical gadgets at once.

The attacks caused the worst damage so far in the conflict, leaving millions of people with no light, water or heat. National power grid operator Ukrenergo said several hours earlier that 30% of electricity supplies were still out, and asked people to cut back on their energy use. "Repairs crews are working around the clock," it said in a statement on Telegram.

Zelenskiy went to the town of Vyshhorod just north of Kyiv on Friday to look at a four-storey building damaged by a Russian missile. We will overcome all challenges and we will definitely win" he said.

Moscow says the attacks on basic infrastructure are militarily legitimate and that Kyiv can end the suffering of its people if it gives in to Russian demands.

"Millions are being plunged into extreme hardship and appalling conditions of life" said U.N. human rights chief. Russia says it does not target civilians in the "special military operation". International human rights officials say that is difficult to reconcile with attacks on civil infrastructure.

Russia is first and foremost about people, their culture, their traditions and their history, President Vladimir Putin has said in a televised meeting with mothers of Russian soldiers killed in Ukraine. Moscow says it launched its operation in Ukraine to protect Russian speakers from what it calls an "artificial country carved from Russian territory".

Putin said he shared the women's' pain, telling them that "the main guarantee of our success is our unity".

The Ukrainian government says 15 people have been killed and 35 wounded in the last six days. Cleverly, who met Zelenskiy on the trip, condemned Russia for its "brutal attacks" on civilians, hospitals and energy infrastructure.

Hungary's President Katalin Novak was travelling to Kyiv to meet Zelenskiy, Hungarian news website index.hu reported on Friday. Kyiv says Russia has incessantly shelled Kherson, the southern Ukrainian city that it abandoned earlier this month.

The International Atomic Energy Agency said the three nuclear plants on Ukrainian-held territory had been reconnected to the grid, two days after the attacks forced them to shut for the first time in 40 years.

The fourth station, in Zaporizhzhia, is in Russian-controlled territory. It came back online on Thursday.

Kyiv says the war reflects what it sees as malice towards Ukrainians dating back to Soviet and imperial days.

This week, Ukrainians will observe the 90th anniversary of the Holodomor famine.

In November 1932, Soviet leader Joseph Stalin dispatched police to seize all grain and livestock from newly collectivized farms, including the seed needed to plant the next crop.

Millions of Ukrainian peasants starved to death in the following months from what Yale University historian Timothy Snyder calls "clearly premeditated mass murder."

Germany's Bundestag parliament is expected to vote overwhelmingly to recognize it as a genocide, following similar moves this week by Romania, Moldova and Ireland.

Russia rejects accusations that the deaths were caused by a deliberate genocidal policy, saying Russians and other ethnic groups had also suffered because of the famine.