Ukraine's President Volodymyr Zelenskyy said his forces would not yield "a single centimetre" in battles for the eastern Ukrainian region of Donetsk, while Russian-installed officials said Ukrainian forces were moving into a southern town with tanks.The focal points of the conflict in the industrial region of Donetsk are around the towns of Bakhmut, Soledar and Avdiivka, which have seen the heaviest fighting since Russian forces invaded Ukraine in late February.Vitaly Kim, the Ukrainian governor of the Mykolaiv region, apparently quoting an intercepted conversation between Russian servicemen, suggested that Ukrainian forces had already pushed the Russians out of the area."Russian troops are complaining that they have already been thrown out of there," Kim said in a statement on his Telegram channel.Ukrainian forces have been on the offensive in recent months while Russia is regrouping to defend areas of Ukraine it still occupies, having called up hundreds of thousands of reservists over the past month."