Burned-out building in Mariupol
Burned-out building in MariupoliStock

The mayor of the Ukrainian port city of Mariupol said Monday that more than 10,000 civilians have died in the Russian siege of his city, and that the death toll could surpass 20,000.

Speaking with The Associated Press, Mayor Vadym Boychenko also accused Russian forces of having blocked weeks of thwarted humanitarian convoys into the city in an attempt to conceal the carnage there from the outside world.

Mariupol has been cut off by Russian attacks that began soon after Russian President Vladimir Putin launched the invasion of Ukraine in late February, and has suffered some of the most brutal assaults of the war.

Boychenko gave new details of recent allegations by Ukrainian officials that Russian forces have brought mobile cremation equipment to Mariupol to dispose of the corpses of victims of the siege.

Russian forces have taken many bodies to a huge shopping center where there are storage facilities and refrigerators, Boychenko told AP.

"Mobile crematoriums have arrived in the form of trucks: You open it, and there is a pipe inside and these bodies are burned," he added.

Meanwhile on Monday, reports suggested that chemical weapons were used in Mariupol.

Ukrainian President Volodymyr Zelenskyy later warned that Russia could use chemical weapons in Ukraine and called on the West to impose strong sanctions on Moscow that would deter even talk of the use of such weapons

Russia recently claimed that Ukraine is running chemical and biological labs with US support.

White House press secretary Jen Psaki later rejected the claims from Russia as "false" and "preposterous," and warned they could serve as a pretext for the Russians to deploy chemical weapons in their assault on Ukraine.

US President Joe Biden then said that Russian accusations that Kyiv has biological and chemical weapons are false and illustrate that Russian President Vladimir Putin is considering using them himself against Ukraine.

Zelenskyy also insisted that no chemical weapons or other weapons of mass destruction were developed in his country.

"No chemical or any other weapons of mass destruction were developed on my land. The whole world knows that. You know that. And if Russia do something like that against us, it will get the most severe sanctions response," he said.