Kyiv, Ukraine(CNN) The race to restore power to homes in Ukraine is being slowed by "strong winds, rain and sub-zero temperatures," the state energy supply company said in a statement on Friday.
"The pace of restoration [to household consumers] is slowed down by difficult weather conditions," Ukrenergo said, with the damage caused by Wednesday's large-scale Russian missile strike, "made worse by the freezing and rupture of wires in distribution networks."
It is the second day of desperate work to keep Ukraine's lights on.
Most power plants are now supplying energy to the national grid after they were temporarily shut down on Wednesday when Moscow sent a barrage of missiles to target energy "generation facilities" in its latest effort to cripple Ukrainian infrastructure, Ukrenergo said. Power has been restored to "critical infrastructure facilities in all regions: boiler houses, gas distribution stations, water utilities, sewage treatment plants."
However there is still a deficit of electricity in the system and Ukrainian authorities are engaged in the delicate work of trying to balance the national power grid, leaving many households without electricity.
As repair teams worked desperately to repair the damage late on Thursday, President Volodymyr Zelensky sought to reassure the many Ukrainians facing a second night without heat, power or water. "The situation with electricity remains difficult in almost all regions. However, we are gradually moving away from blackouts and every hour we return power to new consumers," he said in his nightly video address, in what he described as a "truly national task."
In the Ukrainian capital Kyiv, residents woke up to a thick blanket of fog and temperatures that hovered just above freezing.
"I woke up cold. The heating and electricity are off, again. Water is there. But it might not last," Tymofiy Mylovanov, a presidential adviser and head of the Ukrainian School of Economics, said on Twitter. He, "quickly plugged in power banks, phones, computers to charge" when the power to his apartment briefly came back on in the middle of the night. "I switched on our electric heater. My wife was half asleep but she managed to tell me what I can quickly cook."
Half of people were without power on Friday morning, the Kyiv city military administration wrote on Telegram, and mayor Vitalii Klitschko said only one in three houses had heat. Klitschko said engineers would supply electricity to consumers in turns, for three hours, during the day.
Sergey Kovalenko, head of the YASNO energy company that supplies Kyiv, pleaded with people to be "patient," saying: "We are talking about hours, not days, and especially not weeks." Kovalenko said he hoped to give all residents a few hours of power on Thursday. "The power supply networks will try to evenly distribute the hours of electricity to everyone. That is, around 3-4 hours of power and then an 'exchange,'" he said.
The attack killed at least 10 people, including a teenage girl, and "led to the temporary de-energization of all nuclear power plants, and most thermal and hydroelectric power plants," the Ministry of Energy said. It left much of the country without power, with knock-on effects on heating, the water supply and internet access in some areas.
Wednesday was the first time that Ukraine's four nuclear power plants were simultaneously shut down in 40 years, the head of state nuclear energy company Energoatom said in a statement. Petro Kotin said it was a precautionary measure and that he expected they would be reconnected by Thursday evening. The three fully functioning plants in Ukrainian hands -- the occupied Zaporizhzhia plant has not been operating since September -- would help supply electricity to the national grid, he said.
Ukraine is heavily dependent on nuclear energy, according to the World Nuclear Association. It has 15 reactors at four plants that, before Russia's full-scale invasion in February, generated about half of its electricity.
Russia has turned its attention to destroying energy infrastructure in Ukraine ahead of the bitter winter season, and successive waves of strikes have left much of the country facing rolling blackouts.
The UN Human Rights Chief said Friday that millions of Ukrainians are being "plunged into extreme hardship and appalling conditions of life" because of Moscow's repeated strikes on energy facilities, adding: "Taken as a whole, this raises serious problems under international humanitarian law, which requires a concrete and direct military advantage for each object attacked."
The UN Human Rights Monitoring Mission in Ukraine has confirmed the deaths of 77 civilians since it says Russian "began its ongoing barrage of missile strikes and loitering munition attacks" on October 10.
Wednesday's strike caused havoc across the country, with the capital Kyiv, the western city of Lviv and the entire Odesa region in the dark.
People who had taken shelter from the airstrikes in the capital left bunkers to find their homes without power and scrambled to find a place for the night with friends or family. One in four homes in the city was still without electricity Thursday morning. While the water supply was restored to all districts by mid-afternoon, it was still not working at full capacity, with those in high-rise buildings experiencing low water pressure, Mayor Vitalii Klitschko said.
Video from the Reuters news agency showed people in the capital queuing to collect water from public wells in the pouring rain.
Hospitals relied on generator power or even head torches worn by staff as they continued to perform operations.
In one Kyiv hospital, doctors were performing heart surgery on a child when the power went out. Dr. Borys Todurov posted a video on Instagram that showed surgeons working by the light of their headlamps as they waited for the generator to kick in.
The director of a hospital in the central Dnipropetrovsk region, said "tens of patients in a critical condition were on surgery tables at Mechnikova Hospital" when the blackout hit.
"Anesthesiologists and surgeons put on headlights to save each of them," Dr. Sergii Ryzhenko wrote on Facebook. He posted a photo of two doctors, who he said were Yaroslav Medvedyk and Kseniya Denysova, operating on a 23-year-old man when the electricity went down -- "for the first time in 35 years of Yaroslav's practice."
Zelensky requested an urgent meeting of the UN Security Council following the strikes, which met with swift condemnation from Ukraine's allies.
The European Union announced it would prepare a ninth package of sanctions against Moscow, in what European Commission President Ursula von der Leyen said was an attempt "to blunt even further its capacity to wage war on Ukraine."
French President Emmanuel Macron said Russia's attack demanded a response. "Ukraine suffered massive shelling today, leaving much of the country without water or electricity. Strikes against civilian infrastructures are war crimes and cannot go unpunished," he tweeted on Wednesday night.
Poland said Wednesday the Patriot missile defense system that Germany had offered Poland should go to Ukraine instead. "After further missile attacks (from Russia), I turned to (Germany) to have the proposed (Poland) Patriot batteries transferred to (Ukraine) and deployed at the western border," Polish Defense Minister Mariusz Blaszczak said on Twitter. Germany's offer to Poland came after a missile hit Polish territory near the Ukrainian border on November 15, killing two people.
Kremlin spokesman Dmitry Peskov said Thursday that Ukraine's leadership could stop the suffering by meeting Russia's demands.
"The leadership of Ukraine has every opportunity to bring the situation back to normal, has every opportunity to resolve the situation in such a way as to fulfil the requirements of the Russian side and, accordingly, stop all possible suffering of the local population," Peskov said in a call with reporters.
Meanwhile, Ukraine's defense ministry sent a tweet Thursday marking nine months since Russia's February 24 invasion.
"Nine months. The amount of time in which a child is born. In nine months of its full-scale invasion, Russia has killed and injured hundreds of our children, kidnapped thousands of them, and made millions of children refugees," it said.