The scope of Russia’s devastating modern-day sack of Mariupol has come into renewed and frightful focus as President Zelensky said he believed that “tens of thousands” of people have been killed in the port city and that the Russians used “mobile crematoriums” to dispose of some of the dead. 

The president’s assertions yesterday cast an even darker light on some of Russia’s tactics in its war on Ukraine, and are likely to spark international outrage that will make it difficult for Vladimir Putin to deflect the charge that forces under his command are waging a campaign of genocide in Ukraine.

Mariupol’s mayor, Vadym Boychenko, told the Associated Press yesterday that the death toll in his city may surpass 20,000, which would be in line with Mr. Zelensky’s shock assessment. Underscoring the slide toward depravity after several weeks of relentless attacks by land, sea, and air, Mr. Boychenko claimed that “mobile crematoriums have arrived in the form of trucks: You open it, and there is a pipe inside and these bodies are burned.”  

The mayor told the AP he based his description of the alleged methodical burning of bodies by Russian forces in the city on the assertions of several sources, but did not offer further details.

“The Russians completely destroyed Mariupol and burned it to ashes,” Mr. Zelensky said while speaking to South Korean lawmakers via videolink. “At least tens of thousands of Mariupol citizens must have been killed.”

Mr. Boychenko’s telling of the tragedy unfolding in the city was more graphic: He said civilian corpses are “carpeted through the streets.”

He said Russian forces have taken many bodies to a shopping center where there are storage facilities and refrigerators. It is at that site, it would appear should the allegations prove truthful, that the Russians have been burning the bodies.

Mr. Boychenko also accused Russian forces of having blocked weeks of attempted humanitarian convoys into the city in part to conceal the carnage. 

There are also multiple unconfirmed reports of the use of chemical agents on civilians in Mariupol. Speaking to Sky News, Britain’s armed forces minister, James Heappey, warned that if these accounts were true, Britain and its allies would respond to any deployment by Russia of chemical weapons. 

“Let’s be clear, if they are used at all then President Putin should know that all possible options are on the table in terms of how the West might respond,” Mr. Heappey told Sky News’s Deborah Haynes. 

Ukraine’s deputy defense minister, Anna Malyar, told Liga, a Ukrainian news website, that “you need to understand that the risk of chemical weapons being used does exist, and it is quite high.” 

Via Telegram, Ukraine’s Azov Regiment said “the victims of the poisonous substance spreading of unknown origin in the city of Mariupol are in a relatively satisfactory condition.” The post said civilian contact with the “was minimal … the military were a little bit closer. However, it is impossible to investigate the scene of crime due to enemy fire.”

Before the war Mariupol was a city synonymous with industry and cultural diversity. The calamity of its destruction, from the ugly big picture to the awful small details, will emerge as one of the chief horrors of Vladimir Putin’s unprovoked warmongering in Ukraine. 

The discovery of large numbers of apparently massacred civilians after Russian forces retreated from cities and towns around the capital, Kyiv, already has prompted widespread condemnation and accusations that Russia is committing war crimes in Ukraine.