Ukrainian officials said the targets of the retaliatory attacks included water facilities and a thermal power station in Kharkiv, and that they caused widespread blackouts.
“No military facilities, the goal is to deprive people of light and heat,” Ukrainian President Volodymyr Zelensky wrote on Twitter late on Sunday, reports Reuters.
The US ambassador to Ukraine, Bridget Brink, also denounced the strikes.
“Russia’s apparent response to Ukraine liberating cities and villages in the east: sending missiles to attempt to destroy critical civilian infrastructure,” Brink tweeted.
Moscow denies its forces deliberately target civilians.
Zelensky has described Ukraine’s offensive in the northeast as a potential breakthrough in the six-month-old war and said the winter could see further territorial gains if Kyiv received more powerful weapons.
In the worst defeat for Moscow’s forces since they were repelled from the outskirts of the capital Kyiv in March, thousands of Russian soldiers left behind ammunition and equipment as they fled the city of Izium, which they had used as a logistics hub.
Ukraine’s Chief Commander, General Valeriy Zaluzhnyi, said the armed forces had regained control of more than 3,000 square km (1,158 square miles) since the start of this month.
Near the Russian border, in the village of Kozacha north of Kharkiv, Ukrainian soldiers and local officials were greeted by residents with hugs and handshakes.
“Kozacha (Lopan) is and will be Ukraine. No ‘Russian World’ whatsoever. See for yourselves where the ‘Russian World’ rags are lying around. Glory to Ukraine, glory to the Ukrainian Armed Forces,” district Mayor Vyacheslav Zadorenko said in a video he posted on Facebook.
Moscow’s almost total silence on the defeat – or any explanation for what had taken place in northeastern Ukraine – provoked significant anger among some pro-war commentators and Russian nationalists on social media. Some called on Sunday for President Vladimir Putin to make immediate changes to ensure ultimate victory in the war.
Zelensky said late on Sunday that Russian attacks caused a total blackout in the Kharkiv and Donetsk regions, and partial blackouts in the Zaporizhzhia, Dnipropetrovsk and Sumy regions.
Mykhailo Podolyak, an adviser to Ukraine’s president, said Kharkiv’s CHPP-5 electricity station – one of the largest in Ukraine – had been hit.
“A coward ‘response’ for the escape of its own army from the battlefield,” he said on Twitter.
Kyrylo Tymoshenko, the deputy head of the president’s office, posted an image on Telegram of electrical infrastructure on fire but added power had been restored in some regions.
Ukraine’s gains are important politically for Zelensky as he seeks to keep Europe united behind Ukraine – supplying weapons and money – even as an energy crisis looms this winter following cuts in Russian gas supplies to European customers.
‘Snowball rolling down a hill’