Ukrainian President Volodymyr Zelensky demanded the United Nations punish Russia for air strikes on civilian infrastructure, after a missile barrage plunged cities into freezing darkness in the worst nationwide power outages yet.
With temperatures falling below zero, authorities were working on Thursday to get the lights and heat back on. Russia's latest missile barrage killed 10 people and shut down all of Ukraine's nuclear power plants for the first time in 40 years.
Regional authorities in Kyiv said power had been restored to three quarters of the capital by Thursday morning and water was working again in some areas. Transport was back up and running in the city, with buses replacing electric trams.
Authorities hoped to restart the three nuclear power plants in Ukrainian-held territory by the end of the day.
Most power restored in capital after worst outages so far
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Kyiv aims to restore nuclear plants by end of Thursday
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Since early October, Russia has launched huge barrages of air strikes around once a week at energy targets across Ukraine, each time firing hundreds of millions of dollars worth of missiles to knock out Ukraine's power grid.
Moscow acknowledges attacking basic infrastructure, saying its aim is to reduce Ukraine's ability to fight and push it to negotiate. Kyiv says such attacks are clearly intended to harm civilians, making them a war crime.
"Today is just one day, but we have received 70 missiles. That's the Russian formula of terror. This is all against our energy infrastructure," Zelensky said overnight via video link to the UN Security Council chamber. "Hospitals, schools, transport, residential districts all suffered."
Kremlin spokesman Dmitry Peskov said it was Kyiv's fault Ukrainians were suffering because it refused to yield to Moscow's demands, which he did not spell out. Ukraine says it will only stop fighting when all Russian forces have left.
"What is there to talk about? I think that the first step should come from them. For starters, they have to stop shelling us," said 27-year-old Olena Shafinska, queuing at a water pump in a park in central Kyiv with a group of friends.
For the first time, the Russian attacks forced Kyiv to switch off the three nuclear power plants it still controls. The fourth, in Russian-held territory, also had to activate backup diesel power. Nuclear officials say interruptions in power can disrupt cooling systems and cause an atomic disaster.
"There is a real danger of a nuclear and radiation catastrophe being caused by firing on the entire territory of Ukraine with Russian cruise and ballistic missiles," Petro Kotin, head of Ukraine's nuclear operator Energoatom said.
"Russia must answer for this shameful crime."
Winter has arrived abruptly in Ukraine and temperatures were well below freezing in the capital, a city of three million. US Ambassador to the UN Linda Thomas-Greenfield said Russian President Vladimir Putin was "clearly weaponising winter to inflict immense suffering on the Ukrainian people".
The Russian president "will try to freeze the country into submission," she added.
There was no prospect of action from the Security Council, where Russia wields a veto. Moscow's UN ambassador, Vasily Nebenzya, said it was against council rules for Zelensky to appear via video, and rejected what he called "reckless threats and ultimatums" by Ukraine and its supporters in the West.
He blamed damage to Ukraine's infrastructure on its air defence missiles and said the West should stop supplying them.
Ukrainian authorities said three apartment blocks were hit on Wednesday, killing ten people.
"Our little one was sleeping. Two years old. She was sleeping, she got covered. She is alive, thanks be to God," said a man who gave his name as Fyodr, dragging a suitcase as he walked away from a smouldering apartment building hit in Kyiv.
The blackouts also spread to neighbouring Moldova, where authorities said most power was back on by Thursday.
Moscow has shifted to the tactic of striking Ukraine's infrastructure even as Kyiv has inflicted battlefield defeats on Russian forces since September. Russia has also declared the annexation of land it occupies and called up hundreds of thousands of reservists.
The war's first winter will now test whether Ukraine can press on with its campaign to recapture territory, or whether Russia's commanders can keep their invasion forces supplied and find a way to halt Kyiv's momentum.
Having retreated, Russia has a far shorter line to defend to hold on to seized lands, with more than a third of the front now blocked off by the Dnipro River.
"Ukraine will slowly grow in capabilities, but a continued maneuver east of the Dnipro River and into Russian-occupied Donbas will prove to be much tougher fights," tweeted Mark Hertling, a former commander of US ground forces in Europe.
"Ukrainian morale will be tested with continued Russian attacks against civilian infrastructure ... but Ukraine will persevere."
Russia has been pressing an offensive of its own along the front line west of the city of Donetsk, held by Moscow's proxies since 2014. Ukraine says it has killed thousands of Russian troops there and yielded little ground, describing the Russians as hurled into battle with little equipment or training.
Ukraine's general staff said Russian forces tried again to advance on their main targets in Donetsk region - Bakhmut and Avdiivka with only limited success.
Further south, Russian forces were digging in on the eastern bank of the Dnipro, shelling areas across it including the city of Kherson, recaptured by Ukrainian forces this month.
Reuters could not immediately verify the battlefield accounts.
Moscow says it is carrying out a "special military operation" to protect Russian speakers in what Putin calls an artificial state carved from Russia. Ukraine and the West call the invasion an unprovoked war of aggression.