Ukrainian President Volodymyr Zelenskyy said Ukrainian forces were holding key cities in the central and southeastern part of the country Saturday, while the Russians were trying to block and keep encircled Kharkiv, Nikolaev, Chernihiv and Sumy. Also read: Putin warns against Ukraine no-fly zone “We’re inflicting losses on the occupants they could not see in their worst nightmare,” Zelenskyy said. He alleged that 10,000 Russian troops were killed in the 10 days of the war, a claim that could not be independently verified. The Russian military doesn't offer regular updates on their casualties. Only once, on Wednesday, they revealed a death toll of nearly 500. “This is horrible,” Zelenskyy said. “Guys 18, 20 years old ... soldiers who weren’t even explained what they were going to fight for.” Also read: What to know on Russia’s war in Ukraine