The news came after days of apparent incursions from Ukraine south of Kharkiv, the country’s second-largest city, in what could become the biggest battlefield success for Ukrainian forces since they thwarted a Russian attempt to seize the capital of Kiev at the beginning of the almost seven-month war. Russian Defense Ministry spokesman Igor Konashenkov said on Saturday that troops would regroup from the Balaklia and Izium regions in Ukraine’s Donetsk region. Izyum has been an important base for Russian forces in the Kharkiv region, and earlier this week videos on social media showed residents of Balakliya cheering happily as Ukrainian troops moved in. Konashenkov said the Russian move was being made “to achieve the stated goals of the special military operation to liberate Donbas,” one of the regions of eastern Ukraine that Russia has declared sovereign. The withdrawal claim for a concentration in Donetsk is similar to the justification Russia gave for withdrawing its forces from the Kiev region earlier this year when they failed to take the Ukrainian capital. Ukrainian officials earlier on Saturday claimed significant gains in a counteroffensive against Russian forces in the Kharkiv region, saying Ukrainian troops had cut off vital supplies to Izyum. Ukrainian Foreign Ministry spokesman Oleh Nikolenko also suggested that Ukrainian troops had recaptured Kupiansk, a town along the main supply route to Izyum, centered on the Russian front and the site of heavy artillery and other fighting. Nikolenko tweeted a photo showing soldiers in front of a government building in Kupiansk, 73 kilometers (45 miles) north of Izyum. Ukraine’s Security Service of Ukraine a few hours later released a message it said showed its forces in Kupiansk, further suggesting it had been occupied by Ukrainian troops. The Ukrainian military did not immediately confirm the entry into the city, a rail hub seized by Russia in February. Video on social media appeared to show Ukrainian forces on the outskirts of Izyum at a roadside checkpoint. A large statue bearing the name of the city could be seen in the footage. Ukrainian forces did not recognize the city’s occupation. Earlier on Saturday, Britain’s Ministry of Defense told reporters it believed the Ukrainians had advanced up to 50 kilometers (30 miles) south of Kharkiv and described Russian forces around Izyum as “increasingly isolated”. “The Russian forces were probably taken by surprise. The sector was lightly held and Ukrainian units captured or surrounded several towns,” the British military said, adding that the loss of Kupiansk would greatly affect Russian supply lines. The Institute for the Study of War, a Washington-based think tank, also cited Ukraine’s sweeping gains, estimating that Kyiv has seized about 2,500 square kilometers (965 square miles) in its east. The institute said it appeared that “disorganized Russian forces (carried out) in the rapid Ukrainian advance.” They reported images on social media of what appeared to be Russian prisoners seized during the advance around Izyum and surrounding towns. The same report said Ukrainian forces “may collapse Russian positions around Izyum if they cut Russian land lines of communication” north and south of the city. Vladislav Sokolov, the Russian-appointed head of the local administration, said on social media that authorities in Izyum had begun evacuating residents to Russia. The fighting in eastern Ukraine comes amid an ongoing offensive around Kherson in the south. Analysts suggest Russia may have brought troops from the east to reinforce around Kherson, offering the Ukrainians an opportunity to strike a weakened frontline. Ukrainian Defense Minister Oleksii Reznikov told Ukraina TV channel that the Russians had no food or fuel for their troops in the region as Kyiv had cut off their supply lines. “It will be like an avalanche,” he said, predicting a Russian comeback. “A line of defense will shake and fall.” The Ukrainian military was more circumspect about the reported gains, claiming on Saturday that it had taken “more than 1,000 square kilometers” (386 square miles) from pro-Kremlin forces this week. It said that “in some areas, units of the Defense Forces have penetrated enemy defenses to a depth of 50 kilometers,” matching the British estimate, but did not reveal geographic details. Officials in Kyiv have for weeks kept tight-lipped plans for a counteroffensive to retake territory seized from Russia early in the war, urging residents to refrain from sharing information on social media. However, Ukrainian President Volodymyr Zelenskyy said on Friday that Ukrainian troops have recaptured more than 30 settlements in the Kharkiv region since the counteroffensive began. “We are gradually taking control of more settlements, returning the Ukrainian flag and protection for our people,” Zelensky said. He spoke after the Ukrainian governor of Kharkiv said the national flag had been raised over Balaklia, a town retaken by Ukrainian troops on Thursday after six months of Russian occupation. “Balaklia is Ukraine! Today, together with the army, led by the commander of the ground forces Oleksandr Syrskyy, we raised the Ukrainian flag,” Governor Oleh Syniehubov wrote on Telegram. Elsewhere, Ukrainian emergency services said a 62-year-old woman was killed in a Russian missile attack in the Kharkiv region when her house was leveled overnight. Sinyekhubov also accused Moscow of hammering settlements recaptured from Kyiv. In a Telegram post, he said five civilians were treated in the Izyum area, while nine others were injured elsewhere in the area. In the war-torn Donbas region south of Kharkiv, the Ukrainian governor said civilians were killed and wounded overnight by Russian shelling near the town of Bakhmut, a key target of the Russian offensive there. Pavlo Kyrylenko told Telegram that two people were killed and two others were injured in Bakhmut and the neighboring village of Yahidne. Meanwhile, German Foreign Minister Annalena Baerbock arrived in Kyiv on an unannounced visit on Saturday, saying Europe would not tire of helping Ukraine despite Russian President Vladimir Putin’s efforts to increase pressure by withholding energy supplies from states of the European Union. Baerbock said Germany would help Ukraine find and remove mines and other unexploded ordnance left by Russian troops in areas where they have been pushed back by Ukrainian forces. Despite gains made by Ukraine’s armed forces, US Secretary of State Antony Blinken and the head of NATO warned on Friday that Ukraine’s fight against Russia looks set to last for months. Blinken said the war was entering a critical period and urged Western backers of Ukraine to continue their support through a difficult winter. ——— Kozlowska reported from London. Associated Press writer Frank Jordans in Berlin contributed to this report. ——— Follow all AP stories on the war in Ukraine at