Waves of Russian airstrikes rocked Ukraine on Tuesday, with authorities immediately announcing emergency blackouts after attacks from east to west on energy and other facilities knocked out power and, in the capital, struck residential buildings. A senior Ukrainian official, Kyrylo Tymoshenko, described the situation as “critical” and urged Ukrainians to cut back on their power usage and “hang in there.” Power provider DTEK announced emergency blackouts in the capital and authorities announced similar steps elsewhere, too. Kyiv Mayor Vitali Klitschko said authorities have found a body in one of the residential buildings struck there. Read more: Battle for Kherson was D-Day-like watershed: Zelenskyy The barrage of strikes — including with missiles — came as air raid alerts were issued across Ukraine. At least 10 regions and cities reported that they were targeted. The assault followed what have been days of euphoria in Ukraine after one of its biggest military successes in the nearly nine-month Russian invasion — the retaking last week of the southern city of Kherson. As its battlefield losses mount, Russia has in recent months increasingly resorted to targeting Ukraine’s power grid, seemingly hoping to turn the approach of winter into a weapon by leaving people in the cold and dark. Among regions where officials reported strikes were Lviv, Zhytomyr, Khmelnytskyi and Rivne in the west, and Kharkiv, Ukraine’s second largest city in the northeast. Several missile strikes also hit Kryvyi Rih, President Volodymyr Zelenskyy’s native city, according to its mayor, Oleksandr Vilkul. In Kyiv, video published by a presidential aide showed a five-story, apparently residential building on fire, with flames licking through apartments. The city mayor said three residential buildings were struck and that air defense units shot down other missiles. Vitali Klitschko added on his Telegram social media channel that medics and rescuers are being scrambled to the sites of the attacks. Ukraine had seen a period of comparative calm since previous waves of drone and missile attacks several weeks ago. The strikes came as authorities were already working furiously to get Kherson back on its feet and beginning to investigate alleged Russian abuses there and its surrounds. The southern city is without power and water and the head of the U.N. human rights office’s monitoring mission in Ukraine, Matilda Bogner, on Tuesday decried a “dire humanitarian situation” there. Speaking from Kyiv, Bogner said her teams are looking to travel to Kherson to try to verify allegations of nearly 80 cases of enforced disappearances and arbitrary detention it has turned up in the area and “understand whether the scale is in fact larger than what we have documented already.” Read more: G20: As Lavrov watches on, UK PM Sunak criticises Russia’s “barbaric” war The head of the National Police of Ukraine, Igor Klymenko, said authorities are to start investigating reports from Kherson residents that Russian forces set up at least three alleged torture sites in now-liberated parts of the wider Kherson region and that “our people may have been detained and tortured there.” “Mine clearance is currently underway. After that, I think, today, investigative actions will begin,” he said on Ukrainian TV. The retaking of Kherson was one of Ukraine’s biggest successes in the nearly 9-month-old Russian invasion and dealt another stinging blow to the Kremlin. But large parts of eastern and southern Ukraine remain under Russian control and fighting continues. Zelenskyy on Tuesday likened the recapture of the Kherson to the Allied landings in France on D-Day in World War II, saying both were watersheds on the road to eventual victory. Speaking via video link to a Group of 20 summit in Indonesia, Zelenskyy said Kherson’s liberation from eight months of Russian occupation was “reminiscent of many battles in the past, which became turning points in the wars.” “It’s like, for example, D-Day — the landing of the Allies in Normandy. It was not yet a final point in the fight against evil, but it already determined the entire further course of events. This is exactly what we are feeling now,” he said. The liberation of Kherson — the only provincial capital that Moscow had seized — has sparked days of celebration in Ukraine and allowed families to be reunited for the first time in months. But as winter approaches, the city's remaining 80,000 residents are without heat, water or electricity, and short on food and medicine. Still, U.S. President Joe Biden called it a “significant victory” for Ukraine. Speaking on the sidelines of the G-20 summit, Biden added: "We’re going to continue to provide the capability for the Ukrainian people to defend themselves.” In his address to the G-20, Zelenskyy called for the creation of a special tribunal to try Russian military and political figures for the crime of aggression against Ukraine, and the creation of an international mechanism to compensate Kyiv for wartime deaths and destruction. Zelenskyy referred to the G-20 meeting as “the G-19 summit,” adhering to Kyiv’s line that Russia should be excluded from the grouping. “Everywhere, when we liberate our land, we see one thing — Russia leaves behind torture chambers and mass burials. … How many mass graves are there in the territory that still remains under the control of Russia?" Zelenskyy pointedly asked.

As it continued its barrage of the besieged city of Mariupol, Russia demanded that Ukrainians put down their arms and raise white flags on Monday in exchange for safe passage out of town. Ukraine angrily rejected the offer, which came hours after officials said Russian forces had bombed an art school that was sheltering some 400 people. While the fight for control of the strategically important city remained intense, Western governments and analysts see the broader conflict shifting to a war of attrition. Russian Col. Gen. Mikhail Mizintsev said it would allow two corridors out of Mariupol, heading either east toward Russia or west to other parts of Ukraine. Mariupol residents were given until 5 a.m. Monday to respond to the offer. Russia didn't say what action it would take if it was rejected. But Ukrainian Deputy Prime Minister Irina Vereshchuk said no. “There can be no talk of any surrender, laying down of arms. We have already informed the Russian side about this,” she told the news outlet Ukrainian Pravda. “I wrote: `Instead of wasting time on eight pages of letters, just open the corridor.’” Mariupol Mayor Piotr Andryushchenko also rejected the offer, saying in a Facebook post he didn’t need to wait until morning to respond and cursing at the Russians, according to the news agency Interfax Ukraine. The Russian Ministry of Defense said authorities in Mariupol could face a military tribunal if they sided with what it described as “bandits,” the Russian state news agency RIA Novosti reported. Previous bids to allow residents to evacuate Mariupol and other Ukrainian cities have failed or have been only partially successful, with bombardments continuing as civilians sought to flee. Speaking in a video address early Monday, Ukraine’s President Volodymyr Zelenskyy said about 400 civilians were taking shelter at the art school when it was struck by a Russian bomb. “They are under the rubble, and we don’t know how many of them have survived,” he said. “But we know that we will certainly shoot down the pilot who dropped that bomb, like about 100 other such mass murderers whom we already have downed.” Read:Ukraine war is backdrop in US push for hypersonic weapons Tearful evacuees from the devastated Azov Sea port city have described how “battles took place over every street." The fall of Mariupol would allow Russian forces in southern and eastern Ukraine to link up. But Western military analysts say that even if the surrounded city is taken, the troops battling a block at a time for control there may be too depleted to help secure Russian breakthroughs on other fronts. Three weeks into the invasion, Western governments and analysts see the conflict shifting to a war of attrition, with bogged down Russian forces launching long-range missiles at cities and military bases as Ukrainian forces carry out hit-and-run attacks and seek to sever their supply lines. Ukrainians “have not greeted Russian soldiers with a bunch of flowers,” Zelenskyy told CNN, but with “weapons in their hands.” Moscow cannot hope to rule the country, he added, given Ukrainians' enmity toward the Russian forces. The strike on the art school was the second time in less than a week that officials reported an attack on a public building where Mariupol residents had taken shelter. On Wednesday, a bomb hit a theater where more than 1,000 people were believed to be sheltering. There was no immediate word on casualties in the school attack, which The Associated Press could not independently verify. Ukrainian officials have not given an update on the search of the theater since Friday, when they said at least 130 people had been rescued and another 1,300 were trapped by rubble. City officials and aid groups say food, water and electricity have run low in Mariupol and fighting has kept out humanitarian convoys. Communications are severed. The city has been under bombardment for over three weeks and has seen some of the worst horrors of the war. City officials said at least 2,300 people have died, with some buried in mass graves. Some who were able to flee Mariupol tearfully hugged relatives as they arrived by train Sunday in Lviv, about 1,100 kilometers (680 miles) to the west. “Battles took place over every street. Every house became a target,” said Olga Nikitina, who was embraced by her brother as she got off the train. "Gunfire blew out the windows. The apartment was below freezing.” Maryna Galla narrowly escaped with her 13-year-old son. She said she huddled in the basement of a cultural center along with about 250 people for three weeks without water, electricity or gas. “We left (home) because shells hit the houses across the road. There was no roof. There were people injured,” Galla said, adding that her mother, father and grandparents stayed behind and "don’t even know that we have left." Unexpectedly strong Ukrainian resistance has dashed Russian President Vladimir Putin’s hopes for a quick victory after he ordered the Feb. 24 invasion of his neighbor. In recent days, Russian forces have entered Mariupol. But taking the city could prove costly. “The block-by-block fighting in Mariupol itself is costing the Russian military time, initiative, and combat power,” the Washington-based Institute for the Study of War said in a briefing. In a blunt assessment, the think tank concluded Russia failed in its initial campaign to take the capital of Kyiv and other major cities quickly, and its stalled invasion. U.S. Defense Secretary Lloyd Austin said Ukrainian resistance means Putin’s “forces on the ground are essentially stalled.” “It’s had the effect of him moving his forces into a woodchipper,” Austin told CBS on Sunday. In Ukraine's major cities, hundreds of men, women and children have been killed in Russian attacks. In Kyiv, emergency services reported four people killed by shelling not far from the center of the capital Sunday. Loud explosions were heard as a shopping center and cars in a parking lot caught fire, they said. In a video address to the Israeli parliament on Sunday, Zelenskyy urged the lawmakers to take stronger action against Russia. accusing Putin of trying to carry out a “final solution” against Ukraine. The term was used by Nazi Germany for its genocide of some 6 million Jews during World War II. Zelenskyy, who is Jewish, also noted that a Russian missile struck Babi Yar -- the spot in Kyiv where over 30,000 Jews were slaughtered in 1941 by the Nazis — and is now Ukraine’s main Holocaust memorial. Read:Shelter bombed in Ukraine city; war seen entering new phase Zelenskyy later thanked Israeli Prime Minister Naftali Bennett for trying to help find a negotiation track with Russia "so that we sooner or later start talking with Russia, possibly in Jerusalem.” “It would be the right place to find peace if possible,” Zelenskyy said. He also said he'd had a call Sunday with British Prime Minister Boris Johnson to discuss support for Ukraine during this week's summit of the Group of Seven and NATO. The U.N. has confirmed 902 civilian deaths in the war but concedes the actual toll is likely much higher. It says nearly 3.4 million people have fled Ukraine. Estimates of Russian deaths vary, but even conservative figures are in the low thousands. Some Russians also have fled their country amid a widespread crackdown on dissent. Russia has arrested thousands of antiwar protesters, muzzled independent media and cut access to social media sites like Facebook and Twitter.