Ukrainian forces kept pushing north in the Kharkiv region and advancing to its south and east, Ukraine's army chief said on Sunday, a day after their rapid surge forward drove Russia to abandon its main bastion in the area.
President Volodymyr Zelenskyy hailed the offensive 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.
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.
“In the Kharkiv direction, we began to advance not only to the south and east, but also to the north. There are 50 km to go to the state border (with Russia),” he said on Telegram.
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.
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.
Ukraine's gains are important politically for Zelenskyy 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.
Zelenskyy said Ukrainian forces would continue to advance.
“We will not be standing still,” he said in a CNN interview recorded on Friday in Kyiv. “We will be slowly, gradually moving forward.”
‘Snowball rolling down a hill’
Defense Minister Oleksii Reznikov said Ukraine needed to secure retaken territory against a possible Russian counterattack on stretched Ukrainian supply lines. He told the Financial Times that Ukrainian forces could be encircled by fresh Russian troops if they advanced too far.
But he said the offensive had gone far better than expected, describing it as a “snowball rolling down a hill”.
“It's a sign that Russia can be defeated,” he said.
Kyiv-based military analyst Oleh Zhdanov said the gains could bring a further push into Luhansk region, whose capture Russia claimed at the beginning of July.
“If you look at the map, it is logical to assume that the offensive will develop in the direction of Svatove - Starobelsk, and Sievierodonetsk - Lysychansk,” he said.
The head of Russia's administration in Kharkiv told residents to evacuate the province and flee to Russia, TASS reported on Saturday. Witnesses described traffic jams with people leaving Russian-held territory.
Washington appeared to take a cautious public posture, with the Pentagon referring Reuters to Defense Secretary Lloyd Austin's remarks on Thursday about Kyiv's “encouraging” battlefield successes.
Britain's defense ministry said on Sunday that fighting continued around Izium and the city of Kupiansk, the sole rail hub supplying Russia's front line across northeastern Ukraine, which has been retaken by Ukraine's forces.
Power blackouts and cuts in water supply hit several areas of the Kharkiv region on Sunday, regional governor Olegh Synehubov wrote on Telegram. He accused Russian forces of attacking civilian infrastructure sites.
Moscow denies its forces deliberately target civilians.
The governor of the central region of Dnipropetrovsk, Valentyn Reznichenko, said Russian attacks had also knocked out power to several towns. “They are unable to reconcile themselves to defeats on the battlefield,” he wrote on Telegram.
Nuclear reactor shuts down
As the war entered its 200th day, Ukraine on Sunday shut down the last operating reactor at Europe's biggest nuclear power plant to guard against a catastrophe as fighting rages nearby.
Russia and Ukraine accuse each other of shelling around the Russian-held Zaporizhzhia plant, risking a release of radiation.
The International Atomic Energy Agency said a backup power line to the plant had been restored, providing the external electricity it needed to carry out the shutdown while defending against the risk of a meltdown.
French President Emmanuel Macron told Putin in a phone call on Sunday that the plant's occupation by Russian troops is the reason why its security is compromised, the French presidency said. Putin blamed Ukrainian forces, according to a Kremlin statement.
Ukraine reported more Russian missile and air strikes overnight and regional officials reported heavy Russian shelling in the east and south.
Ukraine's southern command said the military situation in the south was “developing dynamically” as territories were retaken there, while the mayor of the southern city of Mykolaiv said nine people had been injured in shelling.