The Russian military has killed 10,000 Ukrainian civilians in the city of Mariupol alone, the city's mayor stated Monday.

Mayor Vadym Boychenko spoke over the phone with the Associated Press on Monday, saying bodies of civilians "carpeted" the streets. Boychenko also alleged that Russians had brought mobile crematoriums to dispose of the bodies and conceal the deaths.

Mariupol has seen some of the heaviest fighting in Ukraine since Russia began its invasion in late February. The city has faced near-constant shelling and is now largely unrecognizable.

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Boychenko's announcement is a sharp increase over earlier civilian death estimates from city officials, which reported 5,000 deaths.

Ukrainian President Volodymyr Zelenskyy stated Monday that the city "is destroyed."

"Tens of thousands of people [are] dead, but Russians are still continuing the military operation," he added.

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A woman on Friday pulls her bags past houses damaged during a fighting in Mariupol.

A woman on Friday pulls her bags past houses damaged during a fighting in Mariupol. (AP/Alexei Alexandrov)

Zelenskyy made the statement during an address to South Korean lawmakers.

President Joe Biden has condemned Russian President Vladimir Putin as a "war criminal" for his actions in Ukraine.

The U.S. and NATO have also condemned apparent war crimes Russia committed in Bucha, Ukraine, a small city outside the capital of Kyiv.

WARNING: GRAPHIC IMAGE

WARNING: GRAPHIC IMAGE: Cemetery workers carry a corpse of a man from a mass grave to be identified in a morgue in Bucha on Sunday.

WARNING: GRAPHIC IMAGE: Cemetery workers carry a corpse of a man from a mass grave to be identified in a morgue in Bucha on Sunday. (AP/Rodrigo Abd)

Disturbing images showed mass graves filled with the bodies of civilians. Russian military forces made no attempts to disguise their actions during their withdrawal, with many noncombatants lying dead in the street with their hands tied behind their backs.

"This guy is brutal," Biden said last week. "What is happening in Bucha is outrageous and everyone has seen it – I think it is a war crime."

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Biden went on to call for an "actual war crime trial" for Putin. He nevertheless disagreed with Zelenskyy's description of the Russia's treatment of civilians as "genocide."

"No, I think it is a war crime," Biden told reporters when asked about Zelenskyy's comments.