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Ukrainian President Volodymyr Zelenskyy on Wednesday mocked Moscow's insistence that the war against his nation was going well, asking how Vladimir Putin could have approved a plan that involved so many Russians dying.
Mr Putin on Tuesday said Russia would achieve all of its "noble" aims and "rhythmically and calmly" continue what it calls a special military operation.
Moscow said on March 25, its most recent update, that 1,351 soldiers had been killed since the start of the campaign. Ukraine says the real number is closer to 20,000.
"In Russia it was once again said that their so-called 'special operation' is supposedly going according to plan," Mr Zelenskyy said in his regular video address.
"But to be honest, no one in the world understands how such a plan could even come about.
"How could a plan that provides for the death of tens of thousands of their own soldiers in a little more than a month of war, come about? Who could approve such a plan?"
Watch: Zelenskyy mocks Putin for saying war is going as per plan
Russia's initial offensive towards Kyiv failed to seize the capital from Ukrainian control and western governments have spoken of low morale among its troops, with Moscow thought to be turning to mercenaries and recruits from a disputed region of Moldova to shore up numbers.
Ukraine is now bracing for a renewed offensive in the south and east of the region as Russia tries to conquer the city of Mariupol to establish a link between the annexed Crimean peninsula and separatist regions of eastern Ukraine.
Mr Putin used his first public comments on the war in a week to say he was confident that his army would achieve its goals in Ukraine, where the Kremlin claims it is neutralising threats to Russia.
But Mr Zelenskyy asked how many dead Russian soldiers would be acceptable to Mr Putin, giving a range of tens of thousands to hundreds of thousands.
Moscow had lost more men in 48 days since the war started than in the 10-year Afghan war from 1979 to 1989, he said.
Mr Zelenskyy said that while some had made fun of the Russians, their failures in the field and inferior technology, their opponents were not all hopeless.
"We must understand that not all Russian tanks are stuck in fields, not all enemy soldiers simply flee the battlefield and not all of them are conscripts who do not know how to hold weapons properly," he said.
"This does not mean that we should be afraid of them. This means that we must not diminish the accomplishments of our fighters, our army."
