The Russian paramilitary group Wagner, whose men are on the front lines in Ukraine, claimed on Friday to have "practically surrounded" Bakhmut, a strategically important city in the east, and called on President Volodymyr Zelenskyy to sound the withdrawal of his troops.The battle for Bakhmut, an industrial city of disputed strategic importance, has been going on since the summer and has led to great destruction and heavy losses on both sides.The city has become a symbol, as it has been the epicentre of fighting between Russians and Ukrainians for months.In recent weeks, Russian forces had advanced north and south of Bakhmut, cutting off three of the four Ukrainian supply routes and making the defenders' position increasingly precarious."Wagner units have practically surrounded Bakhmut, there is only one road left" to get out, Wagner boss Yevgeny Prigozhin stressed on Friday in a video posted on Telegram by his press service.Dressed in combat gear and speaking as a loud explosion could be heard in the distance, Prigozhin called on Zelenskyy -- who had vowed to defend Bakhmut "as long as possible" -- to order Ukrainian troops to withdraw from the city."Give them a chance to leave the city, it is practically surrounded," he said.Volodymyr Zelenskyy had visited Bakhmut in December and had offered the US Congress, during his visit to Washington shortly thereafter, a Ukrainian flag from that part of the front.The Ukrainian military command admitted on Tuesday that the situation in Bakhmut was "extremely tense" in the face of an attempted Russian breakthrough.Zelenskyy noted the same day an increase in "the intensity of fighting" around the city, which had some 70,000 inhabitants before the war.