Russia seized full control of Mariupol earlier this month when more than 2,400 Ukrainian fighters who had been holding out surrendered at the besieged Azovstal steelworks.
Moscow's capture of Mariupol helped it secure full control of the Sea of Azov coast and create a land bridge linking mainland Russia to Crimea, which it annexed from Ukraine in 2014.
Ukrainian President Volodymyr Zelenskiy has described Mariupol as "completely destroyed", but Moscow has pledged to rebuild it.