Russia’s Defense Ministry announced Saturday that it was pulling back troops from two areas in Ukraine’s eastern Kharkiv region where a Ukrainian counteroffensive has made significant advances in the past week.

The news came after days of apparent advances by 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, Kyiv, at the start of the nearly seven-month war.

“The Russian army in these days is demonstrating the best that it can do — showing its back,” Ukrainian President Volodymyr Zelenskyy said in a video released by his office Saturday night. “And, of course, it’s a good decision for them to run.”