Russia carried out another large-scale drone and missile attack on Ukraine its second in four days, Ukrainian officials said Tuesday, once again targeting energy infrastructure during subzero conditions. The strikes appeared to dismiss U.S.-backed peace initiatives as Moscow’s invasion nears its fourth year.

Russia unleashed a massive overnight aerial assault on Ukraine, firing nearly 300 drones along with 18 ballistic and seven cruise missiles across eight regions, President Volodymyr Zelenskyy said. One strike in the northeastern Kharkiv region hit a mail depot, killing four people and injuring at least 10 others. In the Kyiv region, hundreds of thousands of households were left without electricity as freezing weather gripped the country.

Kyiv has endured subzero temperatures for more than two weeks, with daytime readings dropping to minus 12 degrees Celsius. Ice-coated streets, snow-covered sidewalks and the constant hum of generators underscored the city’s worsening energy crisis. Mayor Vitali Klitschko said the latest strikes caused the most severe power outage the capital has experienced so far, leaving more than 500 residential buildings without central heating.

Residents sought warmth wherever possible. Many gathered at government-run “Points of Invincibility,” temporary shelters offering food, heat and electricity. Olena Davydova, a Kyiv resident, said her family had gone nearly two days without power, forcing them to adapt by sharing beds for warmth, storing food outdoors and relying on candles at night.

Elsewhere, friends and relatives crowded into apartments that still had electricity or hot water to charge phones, shower and share warm drinks. City authorities ordered daily hot meals for vulnerable residents and announced bonuses for utility workers laboring around the clock to restore essential services.

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The attack followed another large-scale Russian barrage just four days earlier, which included the rare use of a hypersonic missile. The United States condemned the renewed strikes as a dangerous escalation, accusing Moscow of deliberately targeting civilian infrastructure to deprive Ukrainians of heat and water-a tactic Ukrainian officials call “weaponizing winter.”

In response, Ukraine carried out drone strikes inside Russia, reportedly hitting a drone manufacturing facility in Taganrog. Russian officials said 11 Ukrainian drones were intercepted, though damage was reported. Independent verification of the claims was not possible.