Ukrain military claims it has launched a major counter-offensive to re-occupy the Russian-held region of Kherson, reports BBC.
The region was captured by Russia in the early days of the invasion.
The reported push appears to form part of a long-awaited counter-offensive being launched by Kyiv in an attempt to retake the country's south.
It follows weeks of Ukrainian attacks aimed at cutting off Russian forces there from main supply routes.
Russia's military claims that Ukrainian troops suffered "heavy losses" during an unsuccessful attacking attempt.
The claims by both Ukraine and Russia have not been independently verified.
Kherson became the first major Ukrainian city to fall into Russian hands after troops advanced into the city from the Crimean Peninsula in the opening days of the war.
Early on Monday, Ukraine's Kakhovka operational group in the south said that one regiment of Russian-backed forces had left its positions in the Kherson region. It added that Russian paratroopers providing the back-up had fled the battlefield.
Oleksiy Arestovych, adviser to President Volodymyr Zelensky's head of office, later also said that Ukraine's armed forces "have broken through the frontline in several places".
In his late night video address, President Zelensky issued a stark warning to Russian forces: "If they want to survive, it is time for Russian soldiers to flee. Go home."
In an update early on Tuesday, a spokesman for Ukraine's southern operational command said 13 Russian command posts had been destroyed, as well as three ammunition depots and a crossing over the Dnipro river.
According to Western military sources, Kyiv's strikes are part of a targeted effort to cut off Russian troops on the right (western) bank of the river with the ultimate goal of recapturing the entire Kherson region. A UK defence intelligence assessment said Russia had made significant efforts to reinforce the western bank but most of its units were "likely undermanned and are reliant upon fragile supply lines".
President Zelensky and other top Ukrainian officials have been tight-lipped about details of the reported counter-offensive, urging Ukrainians to be patient.
Responding to the Ukrainian claims, Russia's defence ministry said that Ukrainian troops had attempted an offensive in the Kherson and neighbouring Mykolaiv regions.
The ministry was quoted by Russia's state-run news agencies as saying this operation had failed, and that the Ukrainian troops had "suffered heavy losses".
Bd-pratidin English/Lutful Hoque
