Moscow abandoned its main bastion in northeastern Ukraine, in a sudden collapse of one of the war's principal front lines after Ukrainian forces made a rapid advance.
The swift fall of Izium in Kharkiv province was Moscow's worst defeat since its troops were forced back from the capital Kyiv in March. This could prove a decisive turning point in the 6-month-old war, with thousands of Russian soldiers abandoning ammunition stockpiles and equipment as they fled.
Russian forces used Izium as the logistics base for one of their main campaigns - a months-long assault from the north on the adjacent Donbas region comprised of Donetsk and Luhansk.
The state-run TASS news agency quoted Russia's defence ministry as saying it had ordered troops to leave the vicinity and reinforce operations elsewhere in neighbouring Donetsk.
The head of Russia's administration in Kharkiv told residents to evacuate the province and flee to Russia to "save lives," TASS reported. Witnesses described traffic jams of cars with people leaving Russian-held territory.
The Russian withdrawal was heralded by Ukrainian leaders. "The Russian army these days is demonstrating its best ability - to show its back," President Volodymyr Zelenskiy said in a video address Saturday evening.
Ukraine's armed forces have liberated around 2,000 square kilometres (770 square miles) of territory since a counter-offensive against Russia started earlier this month, he said.
The Russian withdrawal announcement came hours after Ukrainian troops captured the city of Kupiansk farther north, the sole railway hub supplying Russia's entire front line across northeastern Ukraine. Ukrainian officials posted photos early on Saturday of their troops raising the country's blue-and-yellow flag in front of Kupiansk's city hall.