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The Mariupol City Council on Wednesday accused Russian forces of relying on a mobile crematorium to cover up their alleged war crimes in the southeast port city of Ukraine.

Mariupol, which has been partially occupied for weeks, has been the target of one of the most brutal Russian offensives in Ukraine since the invasion began in February. 

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A view of the Mariupol theater damaged during fighting in territory under the government of the Donetsk People's Republic, eastern Ukraine, Monday, April 4, 2022.

"The killers are covering their tracks," the city council said in several social media posts, adding that the Russians have set up "mobile crematoriums."

"Russia’s top leadership ordered the destruction of any evidence of crimes committed by its army in Mariupol," the council added in a translated statement, accusing Moscow of reacting to widespread condemnation over mass civilian killings in Bucha. 

Humanitarian access to the city has been blocked for weeks, with an estimated 160,000 residents unable to evacuate and lacking access to electricity, heating, health care and water, reported the U.K.’s Ministry of Defense. 

Mariupol officials have estimated that roughly 5,000 civilians had been killed, but warned Wednesday that given the size of the destruction caused to the city the death toll could be in the tens of thousands. 

The Kremlin agreed to a cease-fire last week after devastating shelling pummeled the strategically important city for more than a month.

A damaged building is seen, amid Russia's invasion, in Kharkiv, Ukraine March 14, 2022. (Reuters/Oleksandr Lapshyn)

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But evacuation efforts by the International Committee of the Red Cross (ICRC) were stalled over the weekend due to treacherous conditions. 

ICRC said Wednesday it was able to evacuate about 500 people from the city of Berdiansk, roughly 50 miles south of Mariupol, but it is still unable to gain access to those trapped inside Mariupol. 

City officials claimed that Russia is barring humanitarian access to Mariupol because of the number of deceased Ukrainians that remain on the streets. 

The city council further claimed that Russian forces are removing potential witnesses to "filtration camps" – a claim echoed Tuesday by U.S. Ambassador to the United Nations Linda Thomas-Greenfield, who said she has seen "credible reports" supporting such accusations. 

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Dead bodies are placed into a mass grave on the outskirts of Mariupol, Ukraine, Wednesday, March 9, 2022. People cannot bury their dead because of the heavy shelling by Russian forces.  (AP)

Thomas-Greenfield said Ukrainians in these camps were being stripped of their identification cards and passports, along with being separated from their families. 

"The world has not seen the scale of the tragedy in Mariupol since the existence of the Nazi concentration camps. Russia-occupation forces turned our entire city into a death camp," Mariupol Mayor Vadym Boychenko said in a statement translated by Ukrainian news outlet Interfax. "This is the new Auschwitz and Majdanek."

"The world must help punish Putin's monsters," he added. 

Caitlin McFall is a Fox News Digital reporter. You can reach her at caitlin.mcfall@fox.com or @ctlnmcfall on Twitter.

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This material may not be published, broadcast, rewritten, or redistributed. ©2022 FOX News Network, LLC. All rights reserved. Quotes displayed in real-time or delayed by at least 15 minutes. Market data provided by Factset. Powered and implemented by FactSet Digital Solutions. Legal Statement. Mutual Fund and ETF data provided by Refinitiv Lipper.