Russia launched aerial attacks on Ukraine’s energy sector “on a massive scale” overnight into Wednesday, local authorities said, with explosions reported across the country amid intensified bombardments that have left Ukraine in a precarious position while the war grinds into a third winter.

At least three people were injured in the northeastern city of Kharkiv – less than 20 miles from the Russian border – Ukraine’s national police said, adding that residential buildings and civilian infrastructure were damaged in the attack. At least seven missile strikes targeted the city, regional Governor Oleh Syniehubov said.

Russia attacked “the energy sector again on a massive scale,” Ukraine’s energy minister German Halushchenko said on his Facebook page. Ukraine’s energy operator imposed emergency blackouts in several parts of the country, the minister added.

Poland scrambled fighter jets in response to a Russian missile threat in western Ukraine, according to the Polish Operational Command.

Wednesday’s attack follows a deadly Russian strike on the city of Kryvyi Rih on Christmas Eve. At least one person was killed and 17 others were injured after a Russian missile struck a residential building in the city – the hometown of Ukrainian President Volodymyr Zelensky.

And last Friday, at least one person was killed and several embassies were damaged in a Russian missile attack on Ukraine’s capital Kyiv. That attack came a day after Russian leader Vladimir Putin challenged Ukraine to a “duel” in his end-of-year conference, prompting Zelensky to call the Russian leader a “dumbass.”

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