The head of Russia's Wagner mercenary group, Yevgeny Prigozhin, said in a video posted on Tuesday that his forces now control more than 80% of the eastern Ukrainian city of Bakhmut. Wagner fighters have led Russia's months-long efforts to capture Bakhmut, in one of the bloodiest battles in its 13-month-old invasion of Ukraine. The grinding trench warfare and constant artillery barrages have drawn comparisons with World War One due to massive casualties inflicted on both sides. In a video published by a Russian military blogger on the Telegram messaging app, Prigozhin is seen showing on a map of the area how his forces are continuing their encirclement of the now devastated city, which before Russia's invasion had been home to around 70,000 people. "In Bakhmut, the larger part, more than 80% is now under our control, including the whole administrative center, factories, warehouses, the administration of the city," said Prigozhin. He used a red marker pen to highlight the relatively small, mainly residential area of the city that remained to be captured by Russian forces. "There the war continues," he said. Prigozhin has previously made claims about Russian control of the mining city that turned out to be premature but Ukraine has acknowledged the situation in what it calls "fortress Bakhmut" is now very difficult. Britain's defense ministry said last week that Russian forces had seized the west bank of the Bakhmutka River, endangering a key Ukrainian supply route. The Moscow-installed head of the Russian-controlled part of Ukraine's Donetsk province, Denis Pushilin, said during a visit to Bakhmut on Monday that Russian forces now Controlled about 75% of the city. Russia says the capture of Bakhmut will open up the possibility for future offensives across Ukraine, while Kyiv and the West say the now smashed city has only symbolic importance. The mainly Russian-speaking region of Donetsk is one of four that Russia claims to have annexed from Ukraine following what Kyiv and its Western allies say were sham referendums.