Russia redoubled efforts to subdue Mariupol on Tuesday, a day after the Ukrainian government rejected an ultimatum from Moscow to surrender the southeastern port city.
Mariupol has become the focal point of the war, which began one month ago tomorrow, and is under assault from Russian air, ground and naval forces.
The city council said Mariupol has been transformed into “ashes of a dead land”.
In a video address, Ukraine's president Volodymyr Zelenskiy told the Italian parliament that the city was "like Armageddon".
UN secretary general António Guterres said the war is "unwinnable" for Russia. "For more than two weeks, Mariupol has been encircled by the Russian army and relentlessly bombed, shelled and attacked. For what? Even if Mariupol falls, Ukraine cannot be conquered city by city, street by street, house by house."
Human Rights Watch described Mariupol as a "freezing hellscape riddled with dead bodies and destroyed buildings". The city's deputy mayor, Sergei Orlov, told CNN that the bombardment has been continuous, with Russian aircraft dropping 50-100 bombs daily.
Kyiv accuses Moscow of deporting thousands of residents of Mariupol and the separatist regions of Donetsk and Luhansk to Russia, including children who have been separated from their parents.
The capture of Mariupol would provide Russia with a land corridor from separatist-held areas in eastern Ukraine to the Crimean peninsula, which Moscow annexed in 2014.
The conflict has become a war on cities, with Russia concentrating attacks on the capital, Kyiv, and Kharkiv, Mikolaiv and Odesa as well as Mariupol.
The pro-Kremlin newspaper Komsomolskaya Pravda cited defence ministry sources when it published a report that 9,861 Russian soldiers have been killed in Ukraine, and 16,153 others have been wounded; casualties 20 times higher than the official tally. The report was quickly taken off the website.
Western officials said on Tuesday that Russian forces were stalled around Kyiv but making some progress in the south and east.
About a quarter of Ukraine’s population of 41 million people has become refugees or been internally displaced by the war, according to the UN.
US president Joe Biden will travel to Brussels today to attend meetings of the EU, Nato and the G7 tomorrow. His national security adviser Jake Sullivan said further economic sanctions were likely to be imposed on Russia. Mr Sullivan also said the war in Ukraine "will not end easily or rapidly".
The EU is considering an embargo on oil from Russia.
Meanwhile, a Russian court imposed a new nine-year sentence on Tuesday on Alexei Navalny, President Vladimir Putin's main political opponent, who was already in jail.