Moscow ordered troops to withdraw from near the strategic southern Ukrainian city of Kherson in a major setback as a top US general estimated Russia has suffered more than 100,000 killed or wounded since invading its neighbor in February.
Defense Minister Sergei Shoigu on Wednesday announced that Russian forces would retreat from the west bank of the Dnipro River near Kherson in what could be a turning point in the war.
Ukraine reacted with caution, noting some Russian forces remained in Kherson and reinforcements were being sent to the region.
"They are moving out but not as much as would be taking place if it was a full pullout or regrouping," Oleksiy Arestovych, adviser to President Volodymyr Zelensky, said in a video posted online on Wednesday night.
Russian forces were destroying bridges as they left and mining roads, Arestovych said.
"For the moment, we don't know their intentions - will they engage in fighting with us and will they try to hold the city of Kherson? They are moving very slowly," he said.
The significance of Kherson
Kherson city was the only regional capital Russia captured after the invasion and it has been the focus of a Ukrainian counter-offensive. The city controls the only land route to the Crimea peninsula that Russia annexed in 2014 and the mouth of the Dnipro river that bisects Ukraine.
Russian-installed officials have been evacuating tens of thousands of civilians from Kherson in recent weeks.
Ukrainian military analyst Yuri Butusov said the Ukrainian army's use of US-supplied high mobility artillery rocket systems (HIMARS) had made Dnipro river crossings so dangerous that "the defense of Russian positions here has become impossible."
"But let's be clear. The Russian forces will take up defensive positions and it will be able to carry out new attacks. It will be able to maintain its positions on the east bank for a time," Butusiov said in a YouTube video.