Russia announced on Wednesday that it was withdrawing its forces to the eastern side of the Dnieper River in the Kherson region.
The strategically important city of Kherson was the first regional capital in southern Ukraine to be captured by Russian forces after the special military operation began in February.
The order for the retreat came from Russian Defense Minister Sergey Shoigu in a meeting with top military leaders that was broadcast on Russian state television. General Sergey Surovikin, Russia's top commander in Ukraine, had explained that heavy shelling by advancing Ukrainian forces had posed serious threats to the Russian position west of the Dnieper River, where Kherson is.
Defense along the Dnieper barrier frontier is the most expedient option for operations in the zone covered by the special military operation, Surovikin said.
"The decision to defend on the left bank of the Dnieper is not easy, but at the same time we will save the lives of our military personnel and the combat capability of our forces," Surovikin said in a clip aired on state television.
He told Shoigu that the withdrawal of the forces will free up troops for deployment to other active operations.
The withdrawal of about 20,000 troops will enable Russia to consolidate its defensive lines, said Surovikin, adding that the broad river can serve to defend positions.
"Go ahead with the pullout of troops and take all measures to ensure the safe transfer of troops, weapons and equipment to the other bank of the Dnieper River," Shoigu said.
According to The New York Times, Ukrainian officials said there was strong evidence that Russians were withdrawing from the territory they held west of the river, as Ukrainian soldiers entered some front-line villages that had been under Russian control in the morning.
"We have signs they are pulling out", moving heavy equipment first and then infantry, said Roman Kostenko, a Ukrainian army colonel and chairman of the defense and intelligence committee in Parliament.
Advancing Ukrainian forces captured the settlement of Kalininskoye and the city of Snihurivka, northeast of Kherson city, early on Wednesday, further applying pressure on Russian forces around the regional capital.
Also on Wednesday, Alexander Shevchenko, a member of the Russian delegation to the United Nations General Assembly, said Russia is ready to ensure access to nuclear facilities in Sevastopol as part of the implementation of the guarantees to the International Atomic Energy Agency.
The IAEA guarantees are a package of measures used by the agency to make sure that nuclear facilities are used properly and nuclear material is used for peaceful purposes.
"Russia is ready to give access to these facilities upon a corresponding request. These facilities have nothing to do with the implementation of guarantees in Ukraine," he said at a UN General Assembly session dedicated to the IAEA report for 2022.
Separately, Russian President Vladimir Putin will not attend a gathering of leaders from the Group of 20 nations on the resort island of Bali next week, Reuters quoted Indonesian and Russian officials as saying on Thursday.
Putin will instead be represented by Russian Foreign Minister Sergey Lavrov, the officials said.
The Russian president might take part by video conference, though "the format of (his) participation is being worked out," Russia's state news agency RIA Novosti reported, citing a diplomat in the Russian embassy in Indonesia.